Ron,
Thanks for posting the targets, for the information, and for your future search efforts.

I do love those one-hole sub-MOA 50yd groups with the 460gr CEB BBW#13 brass HP NonCon! Both you and Michael are getting sub-MOA one-hole at 2400+ fps with these bullets so most definitely the sweet spot for the .500 caliber is 0.252” freebore on the low-side and 0.375” freebore on the high-side! But definitely 0.252” freebore for 300yd long range accuracy!

Based upon your .510 JAB and .500 Mbogo info, Jeffe should be fine with his 0.510" P-S Freebore for his combo use (milsurp bullets plus brass and copper hunting bullets) desires/requirements. As you’ve noted it likely will not be quite as accurate long range with hunting bullets but should work just fine for up close work.

I reckon that Tanzan plus anyone else who have no intention of using milsurp bullets and who desire maximum hunting bullet accuracy at 300yds will need to purchase a finish reamer with a shorter P-S Freebore specification to accommodate their specific requirements.

Jeffe,
A quick question. Have you obtained AFT certification for the 500 AccRel as a sporting rifle cartridge?

Thanks guys,

quote:

Originally posted by capoward:
0.252” freebore on the low-side and 0.375” freebore on the high-side!

Thats also my idea for the 500 AR Hatting, I am very certain that we will get the velocities we want, no pressure issues and flawless function.. But it`s soon to be confirmed, throat reamer on its way, modified Manson reamer on its way and LW barrels have arrived...

quote:

Originally posted by buffalo:

quote:

Originally posted by capoward:
0.252” freebore on the low-side and 0.375” freebore on the high-side!

Thats also my idea for the 500 AR Hatting, I am very certain that we will get the velocities we want, no pressure issues and flawless function.. But it`s soon to be confirmed, throat reamer on its way, modified Manson reamer on its way and LW barrels have arrived...

All's well that ends well.

I'm considering having the 500 Mbogo reamer's throat shortened to 0.250" instead of 0.500",
for a "500 Mbogo Hatting" instead of "500 Mbogo Tactical."

Consider the throat on the 510 Kayser.
Rich Kayser aka ISS, basically turned the belt off of a .510 Wells.
He had no problems with too short throat.
His P-S freebore length is only 0.177" long (BB caliber)
and has a tight diameter of .510", meant for .509"-caliber bullets, and a 2-degree leade.
Interestingly, his chamber length up to "collar" allows a +.035" over max brass length also:

The Kayser looks nice. A rather straight case wall after getting used to a Rigby, but a nice cartridge for 8000+ ft lbs. booyah.

I'm wondering how to float a question for the forum:

would anyone want to join Capoward and myself in ordering a shortthroated reamer to be kept at McGowen barrels? You could answer on list or send a PersonalMessage.

Someone has to bite the bullet if we want a short throat 500 Accurate Reloading Nyati. I'm still not getting anything under 2" accuracy at 100 yards.

Questions remaining to be answered:
1. fixed pilot or removable?
2. will Jeff keep his no-go, go gauge with McGowen for general use?

quote:

Originally posted by 416Tanzan:
I'm wondering how to float a question for the forum:

would anyone want to join Capoward and myself in ordering a shortthroated reamer to be kept at McGowen barrels? You could answer on list or send a PersonalMessage.

Someone has to bite the bullet if we want a short throat 500 Accurate Reloading Nyati. I'm still not getting anything under 2" accuracy at 100 yards.

Questions remaining to be answered:
1. fixed pilot or removable?
2. will Jeff keep his no-go, go gauge with McGowen for general use?

I'm interested

I am willing to have mine shortened to .510 at no cost to anyone. I am willing, in fact, to redo this as the standard. I am not willing to go any shorter as it WILL increase pressures.

Guys the round is underbore by design at the long length. This has nothing to do with bullet diameter guys, which I think some of you might think. it means, with the proper powder and given length it would be hard but not impossible to overload.

Twist pressure and freebore are all means to achieve higher velocity from smaller cases. When you shorten the neck radically you WILL raise pressure. This isn't a question or a subject of debate, it is a fact. How much is unknown

Rips Mbogo case has a ton more case capacity than the Accrel. The case to look is the 495 a2 in terms of case capacity and bullet. Shooing pistol bullets isn't relevant nor is one off designed bullets. Both over lower bearing surfaces than traditional cup and core bullets. Yes I KNOW we all want to shoot the newer bullets however the case should be safe to use in all Styles of bullets else it is niche.

Most .510 bullets crimp about .800 behind the nose. More or less, except banded mono metal bullets. Those also stick deeper into the case at the same weight. Unless you go under weight you will then consume case capacity and can result is pressure excursions. Some bore rider bullets are bore diameter far longer than they should be.



All in all, if a shorter throat is desired then .510 satisfies that need without risk of a pressure excursion. This case, for a 510, is tiny and the powders are fast. Frankly pistol bullets and ultra custom
Bullets aren't relevant to the overall safety of the round. Take a heavy bullet, have it in the bottom of the mag and perhaps pushed back into the case a bit under recoil and a hot day. You have a recipe for disaster with a short tight throat


I do not "believe" the throat is the single culprit in make ceb bullets swage to .500 as no other bullets do this. I don't know what to believe on that actually. It is amazing.

Would a shorter throat improve accuracy? Could be. Might or even probably. But that is conjecture at this point and I am willing find out. I get about Moa on 2 very different 500 Accrel barrels and guns with woodleighs and hornadys bullets at 3.35" oal.

So, I present that the 500 Accrel could be shortened to .510 freebore and still be a safe overall round


If you guys must, then call it the Hattig with a super short throat. I do not believe that to be as safe as it could be. Higher pressure tiny case and super short throat in the field doesn't fill me with confidence and I will not compromise my ideas of safety for a quarter Moa DGR.


However if y'all at dead set in the super short throat let me know and I won't bother having my reamer cut down and ordering another barrel and doing the work to find out.


Let me know what you want to do. I dont have any hard feelings either way. And yes I am digging in my heels at going way too short IMHO.

Sent from my iPhone so please forgive weird typos and autocorrect

Headspace gauges will work just fine. And i will absolutley share them. As well as reloading dies. Nothing changes on them

Pilot is a matte of taste when we are talking quality barrels

Thanks Jeffe.. We will start testing as soon as we can...
I will remember your recommendations but I must be thick headed - I still cannot understand why the 500 AccRel would be "less safe" with a .250" throat ...??
I know pressures will be higher compared to the 1,25" throated barrel everything else equal, but I think that we will get same velocities just with a smaller powder charge.. Just like RIP did with his 49-10 ... - we should acheive same or slightly more footpounds of energy as the 49-10 ie above 7000 footibs eh?
And if the 500AccRel is not safe with a .250" throat then why is the 416 Rem, 416 Ruger and 416 Taylor safe with a 0.200” length of freebore (48.07% of caliber)?
And the .375 Ruger (Length of P-S Freebore: 0.1248” - 33.28% of caliber)?

Please explain it to me cause I really dont understand the big difference here...??

Thanks..

Ulrik

- and - by the way - not only the CEB bullets were stripped - the Barnes Banded Solids were stripped down to .500" diameter as well....!

Ulrik
With all due respect the 49 of rips design shoots bullets, in the majority, designed for pistols. There are exceptions. Comparing the two is not unlike comparing the 404 to the 444.

The rounds to compare are the 495 Asquare and 50 peacekeeper. Or even the 505 empire.


Longer throats keep pressure down all else being equal. This is an established fact

Same round and load but shorter throat will have a higher pressure.

This, like almost all pressure related issues, is a curve with a rapidly increasing posture slope. In project management we call it the hockey stick or laying down L shaped. As you make the changes there is a range that lots of change is relatively mild. And then you approach
The extreme of zero. This has infinite Pressure so to speak.


If no rifling has least effect on increasing pressure, that is a smooth bore at .510. This is meant to illustrate the far extreme of low pressure change on the left side of the curve. To the right, like a hockey stick laying blade up, is a near vertical curve of zero throat. All pressure curves in reloading share this basc shape. Increases in pressure don't rear in direct increases in velocity as we all know.

Taking the round down to near zero means higher pressure every time. The 458 winnag has a Long throat And the Lott has nil. It is easily possible to make book in the winnag without a pressure excursion. In the Lott with standard throat, you are right in the edge of pressure to make book. However the watts with its longer throat and only .050 longer case can fire that same Lott round and not have a pressure problem. Thank god that it would be hard to fire a watts in a Lott chamber


Let's take the 458 winmag again. There is very little if any, and some reports of gains, when shooting a winnag in the lott chamber. Why? The net effective throat of
The winmag in the Lott chamber is about the same as the basic winmag chamber overall

That's what, over .38 freebore and it is a known accurate


About all the other cases you mention. All of those are MUCH larger cases relative to bore area and are designed to use much SLOWER powders and much slower twists. The reason the acrel is exceptional is it's use of small case faster powder and better twist. The freebore is a safety, just like it is in all rounds.

quote:

Originally posted by jeffeosso:
I am willing to have mine shortened to .510 at no cost to anyone. I am willing, in fact, to redo this as the standard. I am not willing to go any shorter as it WILL increase pressures.

Guys the round is underbore by design at the long length. This has nothing to do with bullet diameter guys, which I think some of you might think. it means, with the proper powder and given length it would be hard but not impossible to overload.

Twist pressure and freebore are all means to achieve higher velocity from smaller cases. When you shorten the neck radically you WILL raise pressure. This isn't a question or a subject of debate, it is a fact. How much is unknown

All bottleneck rifle cartridges can be overloaded if someone uses a powder that is too fast. When someone loads or designs a 338WM no one would add a 2.5 calibre freebore in order to accommodate someone accidentally using 3031 instead of 4350. I don't really understand the special safety issue except to say that loads must be modified in a shorter throat.

quote:

Rips Mbogo case has a ton more case capacity than the Accrel.

Anyway, at least 15.5 grains H2O worth of a ton. Yes, that is more, like the difference between a 338-06 and a 338 WM, or a 375Ruger, already more than the H&H, and a 375RUM.

I did look long and hard at the 500 Mbogo before going with the 500 AccR. the Mbogo is a great cartridge, too. the extra capacity gives it about 1000 ftlbs advantage. However, it would have been carried as an 11 pound CZ. There has been so much talk about the advantages of short, easy handling rifles that I opted for a Ruger hawkeye build. In a light rifle, 8 lbs naked, 9.2 lbs with scope and barrel-lug bedding, I decided that the limited capacity of 7000ftlb loads was something within which I could live.

quote:

The case to look is the 495 a2 in terms of case capacity and bullet. Shooing pistol bullets isn't relevant nor is one off designed bullets. Both over lower bearing surfaces than traditional cup and core bullets. Yes I KNOW we all want to shoot the newer bullets however the case should be safe to use in all Styles of bullets else it is niche.

different styles of bullets require different powder charges, just like in all calibres, no?

quote:

Most .510 bullets crimp about .800 behind the nose. More or less, except banded mono metal bullets. Those also stick deeper into the case at the same weight. Unless you go under weight you will then consume case capacity and can result is pressure excursions. Some bore rider bullets are bore diameter far longer than they should be.


All in all, if a shorter throat is desired then .510 satisfies that need without risk of a pressure excursion. This case, for a 510, is tiny and the powders are fast. Frankly pistol bullets and ultra custom Bullets aren't relevant to the overall safety of the round. Take a heavy bullet, have it in the bottom of the mag and perhaps pushed back into the case a bit under recoil and a hot day. You have a recipe for disaster with a short tight throat

that potential problem would be true of all cartridges. However, in the 500AccR, even with a short throat, that may be less of a problem since powders are available that provide for compressed loads. A compressed load with a good crimp should go a long way in preventing such a problem.

quote:

I do not "believe" the throat is the single culprit in make ceb bullets swage to .500 as no other bullets do this. I don't know what to believe on that actually. It is amazing.

Would a shorter throat improve accuracy? Could be. Might or even probably. But that is conjecture at this point and I am willing find out. I get about Moa on 2 very different 500 Accrel barrels and guns with woodleighs and hornadys bullets at 3.35" oal.

I'm assuming that you get your accuracy with a Hogue stock? My different bullets are ranging from 2" to 4" groups at 100 yards. I have a Boyd's wood stock that I'm willing to bed and try, but since I'll be rebarreling then I will just wait and bed the new barrel+action.

quote:

So, I present that the 500 Accrel could be shortened to .510 freebore and still be a safe overall round


If you guys must, then call it the Hattig with a super short throat. I do not believe that to be as safe as it could be. Higher pressure tiny case and super short throat in the field doesn't fill me with confidence and I will not compromise my ideas of safety for a quarter Moa DGR.


However if y'all at dead set in the super short throat let me know and I won't bother having my reamer cut down and ordering another barrel and doing the work to find out.

Well, I am pretty sure that the 0.25" throat will be accurate. My question concerns the 0.510" freebore. The stats on the 460 Weatherby seem to suggest that Weatherby cut way back to about .375" freebore (if my memory serves from the earlier posts). I would assume that such a reduction was done for the sake of accuracy. It is also common assumption that Weatherby likes to load their rounds up to the max.

quote:

Let me know what you want to do. I dont have any hard feelings either way. And yes I am digging in my heels at going way too short IMHO.

Sent from my iPhone so please forgive weird typos and autocorrect

Jeff, I greatly appreciate all that you have done for developing this cartridge.

As for throat length, I simply want a custom barrel to have a 'guaranteed' sub-MOA capability. I like to have a 200 yard capability but I need full confidence in the accuracy of a rifle to do that.
A couple of years ago my son was in a situation one afternoon where a herd of buffalo were feeding out from the edge of a forest. My son got out to the last bush of cover. They lasered the buff at 200 yards. (I was watching from back in the trees so as not to overload that little bush of cover.) He took the shot because 1) the sticks were solid, and tracker knew how to brace the elbow 2) the 416 was accurate, 3) there wasn't a twig or blade of grass over six inches between them, 4) buff was classic broadside, and 5) the 350 gr TSX bullet had a good BC and velocity. The buffalo went down, though an insurance shot was fired at about 275 yards when the buffalo stood after running from the hit.

What I fear is not overpressure. That is handled through proper load development. I fear spending money on a second barrel and getting 1.5-2.0" accuracy. In choosing between an accurate 416 Rigby and a so-so hohum 500, I will grab the 416 for shooting a buffalo. As everyone always says, shot placement trumps power. I won't take this 500 to Africa until it is shooting well (consistently <MOA, 3 shot) with bullets that I intend to hunt with.

On names I think I like the hunting tone of
500 Accurate Reloading Nyati for the short "hunters' throat." And on Capoward's question, I think I remember you saying that you did not get an ATF 'sporting determination letter'?

Ulrik,
You are not being thick headed, jeffeosso is.
He is still trying to save face over a silly extra inch of free bore.
Ridiculous!
Irrational!
Trumped up horrors!
Trumped up benefits of an inch too much free bore.
At least he is now willing to concede to .510" P-S free bore.
That is some progress.

BTW, the 49-10 shoots primarily newly designed RIFLE bullets, not pistol bullets.
They just happen to be the same caliber as .500" handgun bullet.
Pistol bullets are inaccurate plinkers in the 49-10, mainly due to free bore being excessive in the 49-10 when using handgun bullets!!!

The 49-10 is also loaded longer to 3.6" magazine length (3.590" COL) instead of 3.4" magazine (500AR),
and it shoots 0.3 MOA to 300 yards with 3 shots, and it can do over 7250 ft-lbs.

All that with the "too short" .252" P-S free bore.

416Tanzan:

500 Mbogo: one of the two I have is 9.5 lbs with a 23" barreled CZ 550 Magnum.
I would not want a 500 AR any lighter than that.

Corey
Thanks. We have parallel deve efforts going on right now with Ulrik in short short neck. I think the .510 will be very accurate.

My cases are usualy designed around VERY fast for caliber powders to reduce recoil and maximize the case use. Yes you can imagine extreme conditions of the WRONG powder.

15 grains is a HUGE difference in case capacities. More than 10% Which is more than most magnum vs standard cases. When you start shoving bullets deeper into the case it shows up even more. 15 grains. Wow that actually is a bunch.

Compare the 495 a2 not a pistol bullet shooting round.

quote:

Originally posted by RIP:
Ulrik,
You are not being thick headed, jeffeosso is.
He is still trying to save face over a silly extra inch of free bore.
Ridiculous!
Irrational!
Trumped up horrors!
Trumped up benefits of an inch too much free bore.

Again with the insults. I am asking you to stop this behavior

I'd like to second Jeff's request.

RIP--I respect your knowledge too much, and I even agree with you on the issue of freebore. This isn't a warm fuzzies forum, but more courtesy and space allow everyone to more clearly appraise what they want to do. And we want clear thinking, not emotion when walking around lions and buffalo. Mini-drip backburner adrenaline provides plenty of emotion.

If Jeff wants a 0.510" freebore for including milsurp he can. It probably does provide more safety margin for loads mixed up with a 1.25" freebore. But mixups can be handled by proper labeling.

Some of us couldn't care less for plinking milsurp, but we do want the best hunting bullets available when walking the African forests and in a rifle as accurate as can be. I'd even consider no freebore if that truly is the way 416Rigbys are built.

Interesting phrase
Black swan event

1 outside of regular expectations and surprise event
2 have a big impact
3 inspire of being an outlier event, some will rationalize it in hindsight as if it should have been expected

I has expected some lower theoretical accuracy with shorter bullets. Moa is fine with me for a fifty. What no one has ever seen before is staging the banded bullets. Thats pretty interesting and might even be worth studying itself.

.510 won't be meaurablely in terms of a hunting rifle less accurate than .250 but is, without a doubt, safer.

If you guys want the super short throat great. I haven't been in the least but reluctant to back your choice. There is no asinine behavior around that, only when it is pretended that I am reluctant does this become emotive. Being emotive actually IS touchy feelie but expressed as bitey clawy.

The dies and headspace gauges will work just fine. Even the heads stamped brass. I am very supportive of y'all doing your own thing. That i dont agree with your choice is my opinion. I support you making your choices. I have just asked and we have agreed to call it something else if shorter than .510.

Frankly I can't think of a more adult mature way to handle this disagreement on freebore than this.

Perhaps this thread has run its course, or at least exhausted my willingness to participate if the abuse doesn't stop. If being beaten in public is rips requirement for participating in this thread them I have had enough.

Frankly I dont have to put up with that level of cyber bullying and abusive behavior and I am tired of it. That this has been a repeated action by rip is a bit annoying and tiresome. Yay ron, you finally found a flaw in one of the accurate reloading rounds. Good for you.

quote:

.510 won't be meaurablely in terms of a hunting rifle less accurate than .250 but is, without a doubt, safer.

Jeff, I don't question that the .510" freebore will have lower pressures or allow more powder, other things equal.

My concern is simply accuracy.
If .510" is truly without measurable difference, then I would be good with that, of course. But how do we know that and why did Weatherby shorten their freebore? I'm slow to come onboard with .5" because once done it can't be fixed, but a .25" freebore can easily be lengthened by a good gunsmith.

If the .510" freebore meant going from a .75" group at 100 yards to a 1.25" group at 100 yards, then I would choose the shorter freebore without hesitation. I start to lose confidence in loads as they go over 1.5".

Handloaders are all capable of of tailoring a load and I would expect loads to reach same pressure levels with less powder in a 0.25" throat. The exact number of grains less would be worked out through experimentation.

Jeffe/RIP- I have to say I've avoided this thread for quite awhile. Seems like much ado over nothing! While I've always favored the short throat approach, I too have intentionally created long throats for various nefarious purposes. Basically my interpretation of this thread can be briefly summarized by the following statement. IT IS WHAT IT IS. I'm outta HERE!-Rob

I've learned a lot about freebore and throat chambers thanks to this thread. What are big lessons I have learned is It seems you sould first decide what bullets you are using before throat specs. It's not uncommon to have multiple specs based on use. It also seems that bore riders make their own freebore. With more and more bullets going minimal bearing surface monometal and leaving Lead jacketed behind it seems that unless you are seating far out a 1/3 diameter freebore is the Goldilocks ratio for freebore. Bullets like CEB reduce pressure so that adds to the margin of safety. It seems that you just have to know your shit when you reload and take nothing for granted. I am glad we can all learn some things here even if it gets a bit testy at times.

quote:

Originally posted by Robgunbuilder:
Jeffe/RIP- I have to say I've avoided this thread for quite awhile. Seems like much ado over nothing! While I've always favored the short throat approach, I too have intentionally created long throats for various nefarious purposes. Basically my interpretation of this thread can be briefly summarized by the following statement. IT IS WHAT IT IS. I'm outta HERE!-Rob

In many ways, I concur with Rob on this. This is out of my area of expertise. But I think I might have something to add now from my end. All the B&Ms have standard or short throats. Until last week I have never seen a shear like Buffalo had in all the test work, or recovered bullets from animals. I took a 475 B&M, used it with great results, terminally. I am having a few issues with this particular rifle, that I did not have with the first 475 B&M. 1st, I am getting a sticky bolt lift at the top of opening--No, it's not pressures, top loads running 60000 PSI, and I even dropped a gr for this hunt, so probably at 57-58 K. Now, this caused me some issues with how fast I could run the gun, and would snatch it a bit when working. Zero pressure signs of course, but with this rifle I have also had excessive stretch in the cases that I also did not experience with the 1st 475 B&M. Sam and I THINK, I might have a slight head space issue in this particular gun. Before, I thought maybe it was a flaw in the cartridge design that we did not catch? Right now, I am not sure of any of this. So I will be testing a 3rd rifle over the next few weeks, with these same exact loads to see how the 3rd rifle reacts to them. If there are no issues with the 3rd rifle, then I have a problem with gun #2 that can be solved. If it is a cartridge design issue, then I will drop the 475 from the lineup, and if I take a notion I might mess with it more?

Now, back to this thread. I recovered only a couple of BBW#13s from this 475 in buffalo. The bullets have NO ENGRAVING on them?????? These were both NonCons, and regardless of no engraving on these two bullets, they were dead spot on accurate, and in one case had driven over 4 ft in a redskin, dead straight. I measured these bands yesterday, and they come to .464, and they start off at .474 of course?????

So this is a bit of mystery to me now.

Since these are the first 1:10 twist barrels I have used on any of the B&Ms, I start thinking the twist is too fast? But then, we recovered several bullets from Mark Davids 475 B&M Super Short, and all those had perfect engraving, and not shear???? I have of course tested the BBW#13s designed for the .474s, 450 Solids, 420 NonCons, out of this SAME EXACT run of bullets I am shooting now, and in the Gun #1, they all have engraving, and were perfect??? In all the test work, Super Short or other 475 B&M rifle, all had engraving. I also think back to the Raptor tests with smaller bores, and some of those had 1:8 twist barrels, all have engraving and no shear??? So I question the twist rate theory. I do however think that some of us have jumped on the fast twist rate a little "premature". While it is absolutely proven that the faster twist does indeed, and is a factor in straight line penetration of our solids in big bores, the faster twist rates only really prove their worth with a less than desirable nose profile and meplat size! I cannot prove that a fast twist rate does anything for us with a proper design bullet, meplat size 65% or better, and a proper nose profile. I can prove that from twist rates at least up to 1:20 do stabilize a proper nose profile, and meplat size--BBW#13s, North Forks, and Barnes Banded Flat nose--and as far as I am concerned these bullets can self stabilize. After firing .474s in a .477 barrel-AKA Michaels Win Capsticks--then for the most part the bullets stabilize themselves, with zero engraving on them.

So long throat? Fast Twist? What? Bullets?

Well, looking at the bullets, same batch of brass, same bullet, tested here, no issues, proper engraving?

I will be doing some terminals, testing with two different rifles in my 475 B&Ms, with this same exact loads and bullets to see if I can narrow this down a bit. In my particular case, a long throat has nothing to do with it, that is for sure. I can't tell you, and I have no answer. I may not even have an answer after I test this. It very well may be my gun #2 that is causing a problem, and that is why I mentioned all the things above concerning it. It might be something in that particular barrel? I just do not know.

For my part here, I am not overly concerned at this point with the shearing effect. I am more concerned right now about this gun #2 of mine. After I work with the new gun, #3, then I will know if my issue is rifle related, or cartridge design related, or I hope so. If #3 shows no issues, then I will be sending gun #2 back to Brian to investigate. If gun #3 shows same issues, I will consult with Brian to see what the issue might possibly be? Gun#1 showed zero issues, and is now out of my hands. The .474 Super Short, shows zero issues, and I have particularly grown very fond of that little cartridge.

The shearing effect seems to have had no effect on terminal performance, in the field. None that I could detect anyway. But I will be testing here in the lab under more controlled conditions to learn if it is an issue or not.

Michael

Wow. Thanks MM. that you are getting bore diameter sheer in a short throat is even more amazing. And that penetration isn't an issue.


I will totally accept that too long of a throat could lead to greater than Moa. Some rifles live long throats. My own 257 Roberts wants a full caliber before it will shoot. Reducing to .510 will more than likely snap them into Moa or better. 3/4 Moa potential, to me, isn't worth the risk and limits of a half caliber neck

Mm you are seeing examples of sheering at upper end loads right ?

quote:

the risk and limits of a half caliber neck

But Michael - all your B&M rifles have short throats right? And they are all "underbore" - even more so than the 500 AccRel.. Have you ever had problems / pressure excursions? If not - then I dont see why the 500 AccRel with a short .250" throat is not as safe as any B&M cartridge also with a short throat...??????

Ulrik
He isn't starting from a known longer neck and working down. He had a greenfield to work from.


However even with VERY short throats genus also seeing stripping in some loads. Therefore the shorter neck isn't likely to be the sole issue for stripped bullets. Qed.

This IS obvious. If 8x grains was perfectly safe in the longer neck the pressure WILL BE HIGHER in a shorter neck.

I typed quite a long discussion in the hockey stick curve. Going extremely short from a KNOWN lower startin point WILL have higher pressure for the same load.

.250 is too short to use accrel loads with a .510 MIGHT be.

Jeffe and Buffalo

quote:

But Michael - all your B&M rifles have short throats right? And they are all "underbore" - even more so than the 500 AccRel..

Yes, that statement is very true. This throat business I left up to Brian and JD at SSK. If it works, I don't care, and they do. I asked Brian about these throats some time ago, and think I posted that here somewhere, but all were short, some being even less than 1/2 Caliber as I recall. No, I don't and never have had any issues at all in any way, pressures or otherwise.

I concur, nothing wrong with short throats.

BUT--like I said, this is WAY out of my area of expertise.

Jeffe, absolutely, I have two of the prettiest sheared bullets you ever want to see. They dropped from .474 to .464 caliber on the bands.

Shearing at upper end loads? Honestly, no. The mystery in my 475 B&M? Currently there have been only 3 rifles built in 475 B&M. I still own gun #2 and Gun #3. #2 is the stainless gun I have been using since Gun #1 left the compound. All 475 B&Ms have 1:10 barrels. I did all the terminal work with #1--no shearing effect, zero issues, engraving, excellent performance! I have done NO terminals with gun #2. Gun#2 has some sort of issue as mentioned. Gun#3 has not been fired yet.

Being out of my area, and never having seen this here it will be a process of eliminating certain factors. First, I am not so concerned about the shearing right now. I am more concerned about testing gun #3 with the exact same loads as I am having issues in gun #2. Gun#1 experienced zero issues. If Gun #3 has zero issues like heavy lift at the top of opening, and no case stretch issues, then gun #2 has a head space issue-I think! If both have the same issue then maybe both have the same head space issue and causing the case to stretch, and pushing the slight shoulder forward causing bolt lift issues--This is NOT PRESSURE related. That is a known fact.

After this, I will do terminals with both gun #2 and Gun #3 to see if there is a shear issue with either? If #2 shears, and #3 does not, then I am inclined to believe that there is some issue with this particular barrel in #2. As we know , #1 did not shear. If Both #3 and #2 shear--then I don't know?

I will be working to eliminate some of this over the next couple of weeks.

Effect on terminals? None. Did bullet shear in barrel or Animal? Don't know. Terminals were of zero consequence on the two animals I got these two bullets out of, and like stated, one of those traveled dead straight for 4 ft, a 420 NonCon--.474 caliber!

Today--I don't think it's twist rate, if it was, the other two rifles would be shearing too--Gun #1 and the 475 Super Short. We recovered a few .474 320 gr #13s from the Super Short and all those had perfect engraving. Bullet? I would have experienced more of this here in the test work, and I have never seen it in any of the test work, any caliber, any rifle, any cartridge, regardless of twist, regardless of various throats, never. Throat? No, I don't think so, but all mine are short throats.

If I had to make a wild guess at this point, I would say I have something going on with this Gun #2, something with the barrel itself, out of spec, too large, too small, to rough to something?

These are some things I can eliminate as I test Gun #3 and #2 in the test medium. In the meantime, I will get the throat specs on the 475 B&M from Brian.

Who Knows????? I don't! Not Yet!

Michael

Hey Michael,
This is rather interesting to have the band abrading issue with your .475 caliber B&M cartridge. The 470 Capstick is spec'd with a 1-10" twist rate; unfortunately your M70 Capsticks have overbore barrels or you could easily identify if the 1-10" twist is contributing to the band abrading at higher MV or whether it is a fluke with that specific barrel.

Jeff,
The 500 AccRel is a handloading proposition, I believe everyone who has contributed to this thread has acknowledged that a 1/2-caliber and even a 1-caliber freebore chamber will require much less gunpowder to reach the same pressure levels as the current 1.25" freebore chamber. Perhaps we just need to note this as a 'known value' without need to re-discuss it.

Et al,
This keeps coming up in concersations so perhaps I can put it to rest. Neither Ron's 12.7x68/49-10 or Michael's 500 MDM were designed to use .500 caliber pistol bullets, both were designed to use longer/heavier monometal bullets.

However, Michael's shorter .500 caliber B&M cartridges do work very well with the bullets designed for use in the .500 S&W cartridge; I believe Michael has noted the 50 B&M SS case to be a virtual capacity match to the .500 S&W case. In fact, I shot a very nice 5-shot iron-sight group on a metal plate at 200yds in the summer of 2010 using the 500gr .500 Hornady FNSP bullets that Michael had run through Sam's pointing die to convert them into round nose bullets. Rifle and cartridge used were a WSM length M70 stocked in a very nice AI walnut stock chambered in the 50 B&M cartridge - I believe they were loaded somewhere around 2000-2050 fps from an 18" barrel. Yes I would use that loading to hunt bear with - if I did not have access to CEB, Lehigh, or NF monometal hunting bullets - but I would use them primarily for practice as they are much cheaper bullets to use and they can be loaded to match the trajectory of the much more expensive monometal hunting bullets.

Also to perhaps lay the .500 caliber pistol bullet issue to rest...I have purchased quite a few blemished 500gr .500 Hornady FNSP bullets; I fully intend to run them through a pointing die that Sam made for me and then use them for practice in my .500 caliber 12.7x68/49-10 chambered rifle - primarily for recoil and bolt-speed recycling practice - after I've broken in my barrel and zero'd in on the loadings it likes with the 430gr CEB MTH, with the 460gr CEB BBW#13 HP NonCon (I've not purchased to replacement 450gr'rs yet), and finally with the 500grmCEB BBW#13 FN Solids... Notice I've relegated the 'pistol bullets' to a specific practice scenario as there are much better hunting bullet alternatives - much more expensive as well...

Ok here's my contribution to the latest delimna of the day...

Just wait until my 12.7x68/49-10 is completed in the next couple of months... The barrel is a 1-9" twist rate, same PacNor manufacture same as Michael's and Ron's 1-12" twist rate barrels, so if fast twist rates contribute to band abrading it will definately show in my rifle.

And now overbore capacity? The .510 caliber 500 AccRel, the .500 caliber 500 MDM, and the .500 caliber 12.7x68/49-10 cartridges are not factory loaded cartridges and none are overbore capacity cases at least with their primary range of bullet weights... My perception is as follows - they are either at capacity or at under-capacity with bullets >1.350" length; the 500 AccRel definately is underbore capacity with the very long 570gr TSX bullets. But move down to shorter bullet length, regardless of monometal or C&C construction both cartridges are progressively overbore capacity...

Ok, 1st cup of coffe down, time for a refill... Yes it's late but wife and I had to watch the entire taped Olympics ceremonies after we got home late last night to didn't hit the rack until after 2AM...

Ok I’ve had my 2nd cup of coffee and pondered things for a while so here we go…

Michael is having band abrading issues with the 2nd of this 475 B&M rifles; no issues with the first, issues with the 2nd as well as noted excessive case stretching… So perhaps with this combination we’re getting closer to identifying the point where the combination of chamfer length plus freebore can/will cause abrading of the driving bands of brass construction bullets. Michael has noted the use of 0.375” freebore for his 500 MDM so the question is whether the same freebore is used for the standard length B&M cartridges.

And I believe it was Boomie who noted the amount of freebore traveled by the banded/bore riding CEB BBW#13 bullets.

So here’s the two known scenarios…
500 MDM:
Chamber Data:
Chamber Length to Neck Chamfer: 2.810” (Pure assumption on my part – Not specified by Michael)
Freebore Diameter: 0.501”
Neck Chamfer Height/Length: 0.0147”
Parallel-Sided Freebore: 0.375”
Length from Neck Chamfer to Throat Intersection: 0.3897”
Length from Neck Chamfer to Bore Diameter: 0.6147”
Length to Neck Chamfer/Freebore Intersection: 2.8247”
Length from Bolt Face to Throat Intersection: 3.1997”
Length from Bolt Face to Bore Diameter: 3.4247”
[color:red Cartridge Data: [/color]
Case Specification Length: 2.800”
Case Trim Length: 2.790” (Pure assumption on my part – Not specified by Michael)
Full Band Width CEB BBW#13 Brass Bullets: 0.070”
So here’s the scenario.
Length to Upper Edge Upper Band w/Seated Bullet at Case Trim Length: 2.860”
Distance Between Upper Edge Upper Band w/Seated Bullet to Freebore/Throat Intersection: 0.3397”
Distance Between Upper Edge Upper Band w/Seated Bullet to Bore Diameter: 0.5647”
So here’s what this scenario tells us… The driving band of the brass bullet can travel 0.3397” of freebore without suffering band abrading and while maintaining accuracy < MOA at 50yds. The 500 MDM has not been tested for accuracy beyond 50yds.
And,
12.7x68/49-10:
Chamber Data:
Chamber Length to Neck Chamfer: 2.669”
Freebore Diameter: 0.502”
Neck Chamfer Height/Length: 0.0145”
Parallel-Sided Freebore: 0.252”
Length from Neck Chamfer to Throat Intersection: 0.2667”
Length from Neck Chamfer to Bore Diameter: 0.4958”
Length to Neck Chamfer/Freebore Intersection: 2.6835”
Length from Bolt Face to Throat Intersection: 2.9357”
Length from Bolt Face to Bore Diameter: 3.1648”
Cartridge Data:
Case Specification Length: 2.650”
Case Trim Length: 2.647”
Full Band Width CEB BBW#13 Brass Bullets: 0.070”
So here’s the scenario.
Length to Upper Edge Upper Band w/Seated Bullet at Case Trim Length: 2.717”
Distance Between Upper Edge Upper Band w/Seated Bullet to Freebore/Throat Intersection: 0.2187”
Distance Between Upper Edge Upper Band w/Seated Bullet to Bore Diameter: 0.4478”
So here’s what this scenario tells us… The driving band of the brass bullet traveling 0.2187” of freebore gives zero pressure issues while maintaining < MOA accuracy through 300yds.

At least to me, these two scenarios tell me that 1) a 0.2187” distance between caliber diameter shank/band of the bullet should result in zero pressure issues and zero band abrading issues while delivering <MOA accuracy at 300yds, and 2) a 0.3397” distance between caliber diameter shank/band of the bullet should result in zero pressure issues and zero band abrading issues while delivering <MOA accuracy w/I 50yds and an assumption of at least MOA accuracy at 300yds.

So here I go with assumption #1. According to information provided by Michael he uses the following which I’m presuming has also been used for this 475 B&M cartridge/chamber specification…
475 B&M – Chamber Issue:
Chamber Data:
Chamber Length to Neck Chamfer: 2.620” (Pure assumption on my part – Not specified by Michael)
Freebore Diameter: 0.476”
Neck Chamfer Height/Length: 0.0179”
Parallel-Sided Freebore: 0.375”
Length from Neck Chamfer to Throat Intersection: 0.3926”
Length from Neck Chamfer to Bore Diameter: 0.6026”
Length to Neck Chamfer/Freebore Intersection: 2.2779”
Length from Bolt Face to Throat Intersection: 2.6526”
Length from Bolt Face to Bore Diameter: 2.8626”
Cartridge Data:
Case Specification Length: 2.250”
Case Trim Length: 2.240”
Full Band Width CEB BBW#13 Brass Bullets: 0.069” (Assumption on my part as I don’t have any of the .475 caliber CEB BBW#13 bullets to measure)
So here’s the scenario.
Length to Upper Edge Upper Band w/Seated Bullet at Case Trim Length: 2.309”
Distance Between Upper Edge Upper Band w/Seated Bullet to Freebore/Throat Intersection: 0.3436”
Distance Between Upper Edge Upper Band w/Seated Bullet to Bore Diameter: 0.5536”
So here’s what this scenario tells us… The driving band of the brass bullet can travel 0.3436” of freebore in rifle #1 without suffering band abrading and while maintaining accuracy < MOA at 50yds. However rifle #2 exhibits excessive case stretch (amount of case stretch not identified) and band abrading at of rifle #1 cartridge loading levels. So at whatever additional chamber length rifle #2 has is indicative of the point where band abrading of brass bullets will occur…

I am aware much of this is conjecture as I do not have the specific chamber lengths for the 500 MDM or the 475 B&M chambers so the specification distance that the driving bands may travel before encountering the throat angle may be more than noted in scenario 1 and 3… Or perhaps there is nothing wrong with the chamber specifications of rifle #2 and the issue relates solely to that particular barrel…

So there we go, relative to driving band-bore-riding brass construction bullets … Are we reaching the maximum Neck Chamfer + Freebore length before band abrading raises its ugly head? Or are we identifying that a 1:10” twist rate imparts some additional trauma to the banding that is not imparted with a 1:12” twist rate? Or have we identified a potential second problem barrel having nothing to do with twist rate or Neck Chamfer + Freebore length?

Jim
Here is where I am. I think a caliber neck could improve accuracy. I have no pov or opinion on stripping the bullets. Half a caliber is, well, too dang short. No sorry until there happens to be imperical data then conjecture won't sway me. My mind is made up but I can be convinced.

A caliber neck improved everything without going overboard.

This may be my last post on the matter until we have data. Including data that shows the shorter throat doesn't strip bullets aswell

Not that I am bored with this, but I don't think we can do much without data. Conjecture is kinda fun. But we are seeing now even short necks rounds stripping bullets. Therefore unsolvable without experiments

Jeff,

I understand your position and I definitely agree, a 1-caliber freebore should definitely accuracy over the current 1.25” freebore.

That said, while we all are awaiting Ulrik’s and Hatting’s testing of freebore lengths, commencing at 0.0250” P-S Freebore, we are now collecting empirical evidence of the likely point where band abrading occurs with brass construction driving-band bore-riding bullets.

Michael has had zero band abrading even when fired up to 3000fps MV in his many M70 B&M and 500 MDM rifles up until rifle #2 chambered for the 475 B&M cartridge; plus Michael notes this rifle has excessive case stretching as well as a sticky bolt lift even though pressure levels are below 60000psi. I believe we’re all aware that he regularly runs some of his loadings beyond 65000 psi without issue.

And I do not recollect any other users of the CEB BBW#13 bullets have noted any band abrading with the brass construction bullets in their rifles – but then as I noted on an earlier page of this thread there are very few commercial cartridges that meet or exceed 2200fps and have a 1-caliber or longer freebore; most are <50% of caliber in freebore length.

Michael, should he be willing to do so, can provide the exact freebore length, the chamber length to the neck chamfer intersection, and his cut case length, to identify the 475 B&M chamber specification against which he and Brian will address the chamber issues of rifle #2. Or should he decide to do so, have Brian do a chamber cast of 475 B&M rifle #2 and the new 475 B&M rifle #3 – and if rifle #3 has zero band abrading issues – then Brian can identify exactly the short distance range between rifles #2 and #3 where the brass construction band abrading occurs.

However, assuming my earlier data is close to correct then we’re aware that the band abrading occurred at a length slightly longer than 0.3926” beyond the chamber length to the neck chamfer intersection. While he ran 3000fps with a light weight .500 caliber brass construction driving-band bore-riding bullets at a length slightly shorter than 0.3926” beyond the chamber length to the neck chamfer intersection.

Then Ulrik’s and Hatting’s freebore length testing will verify whether the same short distance range where the brass construction band abrading occurs. If their testing approximates Michael’s and Brian’s findings then we’ve identified the freebore length that we have to stay below to keep from having the band abrading issue.

Just a thought
are the problems we have with CEB # 13 because of "bad" brass?
is the first driving band too small (2mm long)?

2nd question first - the band width has not been an issue to date even 3000fps MV.

1st question second - there has been one instance of a fault within the brass rod that resulted in a bubble cavity within the nose of a bullet but I don't recollect ever reading about an external issue with the bullets. Additionally, .475 caliber and .510 caliber bullets are CNC machined from different diameter rod material which reduces the probability of the brass rod material being the fault.

I agree - Michael has tested a variety of bullets in different calibers and different velocities from very slow to very fast - no brass issues so far...

buffalo,

are are any estimates for the date of the start of testing?

We wish you exciting, safe fun and discoveries.

quote:

Originally posted by hatting:
Just a thought
are the problems we have with CEB # 13 because of "bad" brass?
is the first driving band too small (2mm long)?

The brass consistency was my first thought. Michael states the bullets were from the same run but is the brass bar stock from that run all the same heat or lot number? I think it would be a good means of eliminating one possible variable if the stripped bullets were tested against unstripped fired bullets to see if the physical properties are the same.

Well, I don't know if this will help or not. But in the case of the "Band Shearing" .474s, I have an answer.

Finally today, I was caught up enough with my real job to see if I could start working on sorting out the .474s.

I have some sort of issue, with both my current 475 B&Ms--Both show snappy bolt lift at the top, even when I change powders, even when I drop pressures to the low 50000 mark. This has nothing to do with pressure. Bolt lift is easy, until the top end, then I get a snap over. This is not good in a DGR, and I won't have it. Both are going back to Brian to investigate what the problem is!

I KNEW DAMN WELL I SHOULD HAVE NEVER NEVER NEVER EVER Built a .474 caliber B&M! WHY? I have never had anything but SHIT out of .474 caliber--remember those .477 caliber Capsticks of mine? NOTHING BUT SHIT FROM .474!

Well, when I figured out that I had two problems with bolt lift, not one, then I went ahead and set up a hasty terminal test with the EXACT same bullets I had in Australia.

Recall, I recovered 2 bullets buffalo/redskin, sheared bands, not a stick of engraving on either of them. 420 BBW#13 NonCons. From my stainless 475 B&M.


So, today I tested the same bullets, same box, same loads, right out of left over ammo I brought home from Australia, in both the stainless 475 B&M, Gun #2 and Gun #3, Gunkote rifle.

Testing the Gun #3 first I found I had engraving on those bullets.







Now this is not as deep of engraving as I have seen on some, but engraved none the less.

Here you see the same bullet fired from the Gun #2, stainless version. The two on the right are from animal tissue I recovered. As you can see slick as a babies ass, not a hint of engraving, and all sheared from .474 down to .464.





This load is a 420 BBW#13 NonCon with 74/H-322. In the Gun#2, stainles, this runs 2293 fps, in the Gunkote Gun#3 it runs 2275 fps.


I have the samples from Gun #1, clearing showing engraving as well.


CONCLUSION???????

Well, not twist rate. Not Throat. Not Bullet. It's a crap BARREL I reckon!

All the barrels are PacNor 1:10 twist .474--or supposed to be.

With this being said, and I know it's not twist rate related, I am changing specs on the 475 B&M barrels. We are checking with PacNor now to see if I can get them to make either 1:12 or 1:14 for this. They make a 1:16, and I think I am going to try one on this stainless gun #2 with the band shearing barrel. You remember, we are using Proper Designed bullets, and proper designed bullets TRUMP twist rates!

So now, is this .510 issue really the long throat of the 500 AR??? If it were me, I don't know that I would bet on that anymore! I would be placing my bets on a shit barrel!

But--I have said it, and will say it again, this is WAY out of my area of expertise.

Michael

Fascinating stuff! What the heck would cause one barrel to shear and not another? I'm assuming the same reamer so leade angle should be the same?

Michael,

tiggertate raises an interesting question. Is there any chance that Dan could test the abraded and grooved bullets to determine if the abraded bullets are a different composition? If so that might eliminate future problems by eliminating the use of rod composition that results in abraded bullets.

Another question. I don't recollect whether the abraded band bullets penetrated through shoulder bone but if so could the shoulder bone have caused the abrading?

Just a couple of thoughts...

What's the shank diameter on the bullets? They look to have more than the normal 0.001"-0.0015" clearence between the shank and bore diameter. Presuming your barrels are cut 0.464" bore and 0.475" Grover diameters.

Michael,
this is helpful for resolving the .474 or whatever its real diameter is. Didn't you have some shearing in the 470 Capsticks, too? I remember one of your tests some time ago where you mention no rifling. It would appear that a sloppy overbore barrel allows brass bullets to bang on the riflings and grind themselves down to bore diameter.

However, with the .510" Acc Rel I think that we are dealing with different barrel manufacturers. My inaccurate rifle is US and Buffalo's shearing rifle is something European. I think that the throat is the culprit in this case. Hatting did some measurements, as well, and the barrel was according to spec.

capo--
a shoulder bone would not cause cylindrical, smooth, .010" abrasion. It's the riflings that are doing the grinding in Michael's .474. I'm guessing that overbore barrels don't allow the riflings enough grip, so the bullets pop and slide and the riflings end up grinding. However, in properly bored rifles a long throat would allow brass bullets the same opportunity for grinding, pop, and slide.

Teach me to read your post while wife is pestering me with something else!

Aside from both rifles having the sticky extraction issue, rifle #2 definately has a barrel issue. It appears both need a return trip to Brian!

I'd have him slug the barrel and do a chamber casting of each rifle before he even looked at the rough extraction issues.

Thanks Tan,
I re-read Michael's post after I'd posted and finally identified abraded bands from the Australian hunt And from today's test firing. Lack of attention on my part.

Tanz

I have two 470 Capsticks from WInchester. Both have .477 actual barrels. Most old woodleighs and barnes and other bullets are .472-.4725, scared to death of double rifle barrel strain, as they should be. So these rattle down those bores, copper, brass, makes no difference at all, NOTHING gets engraved in those guns.

And, boys, I don't know about the .510s???? Jeffe did the long throat for a reason, with the bullets he wanted to shoot. We look at the 500 AR different than he did at the time I suppose. Throats are out of my area--this is why I have Brian and JD at SSK, I would be stupid to second guess them. And, so far I have been 100% correct, and never been an issue with whatever throats the B&Ms have. There is zero doubt in my mind about my bad .474 caliber or whatever it might be, barrel. Also, speaking to Brian about this, there could be something down in the barrel that can't be measured by mere mortals. This .474 barrel we have is going back to PacNor, and they are doing some sort of special test that barrel people have????? He told me, I forgot exactly what it was, the only thing that exceeds my lack of knowledge is my lack of interest in that. That is for them to do. I have other priorities to sort out. And, they are the experts on that, not me.

I should have known better than to dick around with .474 to begin with--I have never ever had any good luck with .474, always some shit! I can't tell it's any better than 458 anyway, and it ain't .500 either! Bastard caliber I reckon! But, I am there now, so have to live with it, sort it out, and fix it!

All 475s--Both of them--Headed to SSK to be thoroughly investigated and sorted out.

The bolt lift is my biggest concern, that is on both rifles. That barrel is not a big deal, we know what that is, "Screwed Up"-- LOL............ My priority is to sort that sticky bolt situation out, everything else will fall in place after that.

M