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A while ago there was an on going discussion about a HBC bullet that was going to revolutionize cast bullet shooting, make a BC of .500, shoot accurately out to 1000 yards at 2700 FPS, and lay waste accepted bullet design theory like Sherman through Georgia, what ever happened?? Inquiring minds want to know.
Pat
 
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I wasn't in on the project, but I think you are talking about the 30 caliber spitzer with the long unsupported nose. What I heard was that some people got good accuracy at low velocity but only at low velocity.

Long unsupported noses are generally not a good idea on cast bullets.
 
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The .30HBC (high ballistic coefficient) was designed by Jay Downs (aka Aladin) and produced by Lee Precision. Some shooters, including Jay, have reported high accuracy @ 2,200 - 2,400fps. I haven't been so fortunate. I.e., I've got m.o.a. accuracy, but @ 1,400fps. Higher speeds gave wild shooting: no real groups, flyers, complete misses. When the weather turns a bit more favorable, I'm going to retest the .30HBC sized to .311" and ~50gr. IMR 7383, which performs similarly to IMR 4350 in the '06 (and .243Win.) case.
 
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Pat, you're exagerating a little on it's objectives. We did design it to have a HBC, but we also knew in the process that it would be a challange to everyone who tried it to get everything just right so it would perform. Most of the folks that have had success at higher velocities have done so with VERY hard alloys. There are results posted on several forums, worth the effort to look for (using search functions).


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PS. Look through the SWAGING forum here for some of the research we went through in the design.


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Tim,

Maybe I did sound like a smart a$$ in my original post but I'm not exagerating, it's what the designer stated in this and other forums if I remember right.

I have a little experience with bullet design and long heavy bullets and to tell you the truth I'd have to see the 30 HBC shoot accurately at 2200 to 2400 fps before I'd believe it. It ain't easy to get a normal bullet to shoot well at those velocities let alone one that's not supported for half it's length, and I firmly believe getting anywhere's near a .500 BC with cast is impossible, that's equaling or bettering a 190 gr Sierra MatchKing!

The 30 cal bullet I designed and had Dave Mos cut a while ago is 1.385 long and weighs 250 grs. in wheel weights. I throated the barrel and cut a die to taper the bullet with the same reamer so that the bullet's supported for most of it's length. I found from my experience that with longer than normal bullets and the twists you need to spin them you're limited on velocity. 1750 fps is the best I could get out of it with the accuracy needed to be competitive in CBA matches but it did shoot pretty well and for a while I held the 10 shot 200 yard heavy class aggregate record with it. Through actual testing using the proper equipment it made a BC of .396 at the 1750 it shot best at.

A couple of years ago I cut a 6.5 mould that's 1 1/4 inches long and weighs 170 grs. that I competed with in a Shilen 8 twist barrel. An 1 1/4 170 gr. 6.5 is pretty long and heavy and it came out the same way, at 1750 fps it shot the best. I throated the barrel and made a die the same as the .30 so again the bullet's supported for most of it's length.

I am interested in the results people are getting with the HBC bullet but don't know where to look to find them.

Thanks, Pat
 
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No problem, Pat.

Here's the beginning, I'll chase out a few more on other boards (results).

This was about a year into the project (2 years) and it covers some of the concepts of what we considered.

We knew at the time that we wouldn't be doing a VLD bullet, just one of much better BC than what is typically seen in lead alloy. (Knowing also that there were going to be real reasons one typically did not see a HBC design in lead alloy.)


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oops

http://www.graybeardoutdoors.com/phpbb2/viewtopic.php?t...&highlight=hbc+30210

you might well have to hit REFRESH 5 or 6 times if it doesn't come up right away - as they've been having server problems.


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Let me also note that Aladin has aparently deleted his posts from this thread. Mine remain.


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Here's one. Indirect, though.
http://castboolits.gunloads.com/showthread.php?t=3727&highlight=HBC+30-210


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Here's another.

http://castboolits.gunloads.com/showthread.php?t=2767&highlight=HBC

suggest doing searches on hbc and then on 30-210


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Some 'lively' reading in this one too:

http://castboolits.gunloads.com/showthread.php?t=2328&highlight=HBC

Draw your own conclusions. I look for what several people are successful at and let the rest slide.

Aside from the name calling, it was a fun project - pushing outside the box just a little.


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Thanks Tim, from reading a lot of your past posts you've always proven yourself to be a gentleman. I did expect to see a lot more input considering the amount of moulds sold but maybe that'll come later. Since I'm sure you have one of the moulds yourself have you had any luck with it?

Pat
 
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Pat - thanks. From the # of moulds (about 50 or so) there are likely to be maybe 10 people that will get serious about it. I will admit that even though I did the drawings for it, I have only gotten as far as casting up a small batch. I have a Rem 40X in 7.62 Nato that is slated for cast boolets. At the moment my interests have been diverted to cannons and mortars; but I'm beginning the swing back to cast and scheutzen. So many toys, so little time.


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Pat - thanks again for bringing this up. I cast a few tonight and tried sizing - only to find the alloy a bit soft. Oven heated them & quenched, I'll find out soon if they're hard enough.

(About time I got around to it!)


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Hi Fellas
I just started playin with my HBC lite loads unique at 50 yds feeling it out with the 06. 1 1/4 so far . Didnt Chrony yet. Boon


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Won't happen this weekend. OAL of bullet and gas check unsized 1.295; sized 1.220; oven heated and quenched then sized 1.243". (CORRECTED)

Not hard enough. Too much distortion.
I'll dig out some linotype and try it.

Before I shoot I'll measure runout on loaded round, sort into groups, mark and orient in chamber - just like jacketed bullets at a match.


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Tim,

Please keep me posted on your success (or lack of) with the bullet. A Lee sizer would cure your problem with sizing then run it into an oversize H&I die for lube. If I read your post right the bullet gained .050 in length from just sizing it? I can see losing a little length because of crushing the pointed nose but it sounds weird that it grew so much

I've read a lot of stuff about bullet noses slumping but I don't know if that's a fact or not and can't think of a way to prove it. In my opinion the reason a bullet with so little support won't shoot at speed is because there's no guidance on ignition causing the bullet to enter the bore at an angle knocking it's balance out of whack. I remember looking at the HBC drawing when it was first put out and figured that it'd only have about .015 contact (at best) with the throat of a 30/06 for initial guidance. You have to look at the case neck as an extension of the throat so assuming about 3 or 4 thousandths clearance with the chamber and the nose hanging out there in mid air the thing's at a disadvantage from the start.

I suppose on second thought there might be a way to at least have as better understanding about the bullet slumping theory vs. the lack of support theory and that'd be if someone had a tight necked 06 and seated the bullet against the throat, and hopefully deep in the neck, with maybe .0005 neck clearance to see if it made a difference. I suppose a 308 would be just as good and there'd be a lot better chance of someone having a tight necked 308 but the 06 has a lot longer neck.

Just Rambling, Pat
 
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quote:
Originally posted by Pat I.:
Tim,

Please keep me posted on your success (or lack of) with the bullet. A Lee sizer would cure your problem with sizing then run it into an oversize H&I die for lube. If I read your post right the bullet gained .050 in length from just sizing it? I can see losing a little length because of crushing the pointed nose but it sounds weird that it grew so much

I've read a lot of stuff about bullet noses slumping but I don't know if that's a fact or not and can't think of a way to prove it. In my opinion the reason a bullet with so little support won't shoot at speed is because there's no guidance on ignition causing the bullet to enter the bore at an angle knocking it's balance out of whack. I remember looking at the HBC drawing when it was first put out and figured that it'd only have about .015 contact (at best) with the throat of a 30/06 for initial guidance. You have to look at the case neck as an extension of the throat so assuming about 3 or 4 thousandths clearance with the chamber and the nose hanging out there in mid air the thing's at a disadvantage from the start.

I suppose on second thought there might be a way to at least have as better understanding about the bullet slumping theory vs. the lack of support theory and that'd be if someone had a tight necked 06 and seated the bullet against the throat, and hopefully deep in the neck, with maybe .0005 neck clearance to see if it made a difference. I suppose a 308 would be just as good and there'd be a lot better chance of someone having a tight necked 308 but the 06 has a lot longer neck.

Just Rambling, Pat


Good thoughts. I corrected the #s. Yes it shortened it by pushing through.

Slumping, the fundamental work documenting it is Dr. Mann's book, "The bullet's flight" published in the 1920's - I'll dig out the ISBN.

I'll dig out the drawings on the sammi chamber/bullet engagement into throat.

When I'm concerned about alignment, I'll neck size only half way. That puts the bottom half of the neck of the cartrige very close to the chamber and the top half grips the bullet. With necks outside-turned that's about as close to making the bullet's axis coaxial with the axis of the bore that I can figure out (apart from a bore rider).

I cast a few last night from linotype last night, water quenching from the mould - VERY hard. I'll try sizing/seating the GC tonight. Depending on sorting I may cast more later this week. Rain predicted for the weekend.

This is a good discussion of the issues, thanks.


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Tim,

I reread your letter and see I made the mistake of writing a reply before actually knowing what you said about the bullet length before and after sizing, sorry.

I'm ashamed to say I've never read Dr. Mann's book and probably should. I'd especially like to see the conditions and equipment he used to actually be able to document a bullet's nose slumping. I'm not saying he's not totally correct but I have my own opinions about stuff and it takes a lot to change them (remember I'm a middle aged cast bullet shooter and we all know everything).

There's another thing I firmly believe and that's that a bullet is twist limited as far as velocity goes. Tom Gray wrote up an excellent article about it in the F.S. a few years ago and my personal experience follows much the same path. The faster the twist the slower you have to go. I've chambered and fit 30 BR barrels with 14,13,11, and 10 twists for myself and every time I went faster with the twist to use a heavier bullet the slower I had to go velocity wise to get it to shoot, a Catch 22 for sure. My next try at it is to fit a 17 twist Shilen barrel in 30x47 using about a .900 long bullet to see if I can get it up to 2500 fps with accuracy. Have all the parts just have to get my ass in gear, cut the mould, and put it together.

I know a lot of guys hate BR stuff for some reason but a lot of useful knowledge has come from the guys doing it (myself not included) and believe me we're not a bunch of stuffy old farts. I already told this to Paul Brasky but I work on a truck dock, smoke like a fiend, have tattoos, swear well enough to be in the top 10% of swearers world wide, and have and shoot a lot of other guns besides BR stuff. And I'm not alone in the CBA BR game.

Later, Pat
 
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The SAAMI '06 chamber has a sloppy neck with 0.008" - 0.010" clearance when a 0.308" bullet, so if the pressure rises enough to expand the brass neck (about 8000 psi) while the bullet is still in the case, then the base of the bullet will be hanging out in the wind.

Dr. Mann worked almost exclusively with pure lead bullets. He did some pioneering studies on obturation but I don't recall any mention of slumping. Could be, though, as there is a ton of stuff in his book and it's definitely worth a read. You can find it on ebay from time to time, The Bullet's Flight. He recovered fired bullets intact by firing them into a long box containing oiled sawdust.

It's a free country, so suit yourself, but I've had better luck with cast bullets that are supported from tip to tail.
 
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Poppenman - agree with you on the support of the bullet and accuracy, but the INTENT of this bullet was to see if we could get a high BC - useful at long ranges. The only way I know of doing that is to make it pointed. (See the basis for the calculations on the thread from the swaging forum on GBO).

Mann came to the conclusion (pg 81-82) that the bullet slumps before the nose of the bullet starts to move (see his details of the experiments).

Pat - you weren't wrong; after reading your post I went back and made the correction of the numbers.

The book: The Bullet's Flight, the ballistics of small arms. By Franklin W. Mann. This is a copy of the 2nd edition of The Bullet's Flight from powder to target the internal and external ballistics of small arms - with notes from Harry M. Pope in the margins. Wolfe Publishing Co. P.O.Box 30-30, Prescott, AZ, 86302 c. 1980.
ISBN 0-935632-04-2


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quote:
Originally posted by trk:
Mann came to the conclusion (pg 81-82) that the bullet slumps before the nose of the bullet starts to move (see his details of the experiments).


Mann is talking about what he calls "upsetting" or nowadays called "obturation". That is different, in my mind, from "slumping" where an unsupported and un-obturated nose slumps to one side due to bending or canting.
 
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Tim,

If Mann's talking about obturation I'll agree with him 100% although obturating a bullet all the way to the tip would require some pretty extreme circumstances if you asked me. I always had the impression that when the term "slumping" was used it was referring to the nose of a bullet bending to one side or the other, which I still can't figure out how anyone could prove this. To be honest in my opinion it'd be a blessing for the HBC bullet if the bore riding portion of the nose did obturate enough to contact the lands.

Pat
 
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Obturate, by definition, means to 'block the passage through' or to seal. By slumping, Mann is referring to deformation. He defines it as the movement of metal in the bullet. He goes on to say that if there is an enlargement in the bore in the first 10" that the bullet (lead fired over blackpowder) will fill to that enlargement, but not after 11". This conclusion by experimental observation.

My observation in sizing the WW bullet was that the ogive expanded upon sizing the .313 diameter section to .311 and seating the GC. My concern (because of BC) was that the shape was modified. Slumping to one side or the other would be another issue as well. Super hard bullet (because strength and hardness go together) seems to be an asset for this issue.

The size and angle of the area of contact of the ogive at the throat was designed to match closely to the sammi chamber (I'll have to look, but I think it was the .30-06; there are some differences between .300WM and 7.62N of course, not to mention manufacturing and customization variances). Optimizing the fit at the point of contact was intended to seal (obturate) reducing blowby. Mann addresses the issues of deformation from that point in reference to slumping and expansion of the base dependant upon how much the bullet is supported around it's circumference.


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All, I posted my latest results (not good) with .30HBC on the Gunloads Cast Boolits site. In brief, I sized & heat-treated the .30HBC's (WW + 1% Sn), seated them into the rifling of my Mod. 70 Win. and used 49gr. IMR 7383, the slowest powder I had on hand. Mean velocity was 2,350fps +-15fps. ES was 44. Now for the bad news: 4 of the initial batch of 20 (in LC Match brass) grouped within 2" of each other @ 50 yds. The remainder were all over the target backer. For a control I used 4 Ly. #311291 @ .311" (seated into the rifling) and 4 CBE heavy Loverin (195gr.) @ .311" (seated into the rifling) in new LC '67 brass over 30gr. of whatever powder was used in those Garand rounds. Both of these grouped under 1". Btw, there was no leading with the HBC's or the aforementioned CB's either. Although the .30HBC will give m.o.a. accuracy, I've only been able to achieve it at ~1,600fps or less. Life is too short to waste monkeying with a CB design of questionable value, ergo I'm going to auction the mold on EBay.
 
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Is any of the folks playing with the HBC doing it with a gun that has a true match grade barrel and chamber/throat? I'm thinking out load that the design might work in such an application, but with std slop sporter or milsurp barrels, there are too many things working against the bullet working as desired.


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[QUOTE]Originally posted by trk:
Obturate, by definition, means to 'block the passage through' or to seal. By slumping, Mann is referring to deformation. He defines it as the movement of metal in the bullet. He goes on to say that if there is an enlargement in the bore in the first 10" that the bullet (lead fired over blackpowder) will fill to that enlargement, but not after 11". This conclusion by experimental observation.


Tim,

I'm not sure what you're saying here, are you saying that Mann proved that bullets do slump over or that they are slugged up by pressure to form a seal? As far as deformation goes I suppose a bullet being slugged up would apply since the original form is changed even if for the better.
By the last sentence above it seems that Mann was talking about deformation being the bullet slugging up (obturating) to fit the barrel but I'd like to know what you think.

If Paul Brasky would be willing to sell me his mould I'd be happy to give it a try in my 30 PPC cast bullet gun. It's set up for my heavy bullet (weight is another way to gain BC)and the throat might be a little long, only by trying it would I know. The gun's built on a Stolle action with a 10 twist HV Shilen barrel in a TMBR stock. The neck's .328 with a 22 1/2 degree throat. I'm not the greatest shot in the world but I'd do my best to be honest and fair. I'd use a push through sizer and lube by hand with LBT Blue to not cause any damage to the bullet nose. I use HTWW for my match shooting and that's what I'd use for this since it seems a popular alloy and my pot's filled with it. If I found a good shooting load I'd also set up to test the bullet's BC if anyone was interested.

I have to admit it would be hard to set my prejudice about this bullet aside but I'd do my best to give it a fair shake.

Pat
 
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Pat - I separate the obturation (sealing) at the moment of firing from what Mann says (about the bullet behind the point of contact with the throat - which on his bullets was right up front). Whichever. He specifically was talking about the bullet deforming from the driving pressure from the rear expanding the bullet (soft lead) into any available widening available in the first 10". With his bullets, since they were mostly not pointed but right-much cylindrical, the deformation was from the rear. I'm not aware of (it would take reading through again to see if he addressed it) him talking about the nose slumping. As you raise the issue, that is a different issue.

I think everyone agrees on this one that the ability to align it into the bore correctly is a major issue.

I'm thinking now about not sizing at all (as the sizing process squeezes the grooves tight and I'd like that to happen on firing.

I'd love to see what you come up with - it looks like you've got a serious platform on which to make comparisons.


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Tim,

I get what you're saying now I think. What confused me was that we seem to have a different definition on what obturation is in cast bullet shooting. If I'm reading right I'd consider what you call obturation "bullet fit" and what Mann called deformation or slump "obturation". If I'm wrong again the hell with it, I must be dense!!

Pat
 
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We're getting close. Mann doesn't use the term obturation in these pages. He uses the term 'upset' referring to deformation of the base. It seems that I misspoke and injected the word slump, which would better be used for the nose deformation.

I use the term obturate in the narrower sense (closer to the dictionary defitition) of sealing; hence the critical fit of the bullet to the bore.

Slump, I think we agree refers to the nose deforming.


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quote:
Originally posted by trk:
We're getting close. Mann doesn't use the term obturation in these pages. He uses the term 'upset' referring to deformation of the base. It seems that I misspoke and injected the word slump, which would better be used for the nose deformation.

I use the term obturate in the narrower sense (closer to the dictionary defitition) of sealing; hence the critical fit of the bullet to the bore.

Slump, I think we agree refers to the nose deforming.




Pat & Trk - If I recall correctly, one of the ways bullet nose "enlargement" (from the pressure of propellant gases on its base) has been determined, is by catching bullets in some sort of non-deforming medium, then checking to see if there are any rifling marks on parts of the nose which began their trip too small in diameter to touch the rifling at all.

Sorry for the clumsy long sentence, but it's late in the day....

One other note, A way to get best bore alignment before firing is to use fireformed cases that are thick-necked enough to be "zero clearance to the neck when a bullet of throat diameter is seated. Dave Lee used that method in all his match rifles, as did several others of his shooting buddies. That might be unsafe as Hell with jacketed bullets, but it was no problem with linotype alloy. Guess it is just soft enough to get away with it....


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AC - Yes. Mann first used snow (then sawdust with oil). One might think WHAT? But even before I read his book, in Iowa, in the dead of winter when the rivers were frozen (-10F for 2 weeks). I first discovered it with a .357 shooting tin cans on the frozen river - we walked 50 yards past and found a little rise in the snow (1/2") with a groove in it. Then more, and more, getting closer, curving to the right AND then the bullet encrusted with little crystals of ice sitting on the top of the snow - slowed down a little at a time with no deformation. Picked up a lot those days. Then I tried it with a 6mm or .25-06 ! Had to have the 'targets' 100 yards out and shoot prone, lost most of them, but it even worked with the high velocity bullets.

I like the idea of breach seating, and the idea of making a special casing is good too. With jacketed (6PPC) I have a .264 neck and produce a loaded round at .262 MAXIMUM diameter.

It makes sense that the clearance could be reduced a bit with cast. A thou clearance (each side) may be as close as one could come, depends on how easily the two can be slid together.


I'm going to recast. I had a small bur that caused finning on the nose, and a little variation between weights.


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Pat - I've been digging for the sammi drawings I've got in AutoCAD. On another computer, that is at the moment disassembled.

I'll post bullet-throat matchup drawings.


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quote:
Originally posted by trk:

QUOTE] I like the idea of breach seating, and the idea of making a special casing is good too. With jacketed (6PPC) I have a .264 neck and produce a loaded round at .262 MAXIMUM diameter.

It makes sense that the clearance could be reduced a bit with cast. A thou clearance (each side) may be as close as one could come, depends on how easily the two can be slid together.



TRk - for jacketed bullets, I use the same basic set-up in 6-PPC that you do...262" chamber neck, but I use .2612" loaded ammo necks....0004" per side clearance.

But, what I was referring to with Dave Lee and his shooting pals (not all of them, but several very good competitors) was 0.00" clearance...as in .332" chamber necks and .3321"loaded round necks in the .30-BR....actually, a one ten-thousandth interference fit.

That also works if you have the case neck that size, but have the bullet diameter just enough smaller than the inside diameter of the case neck that the bullet can be seated by hand without using a die. In other words, if you had a .332" chamber and .010" turned neck wall thickness all the way around, you'd use a .3118" or .3119 bullet base (measured over the gas check after sizing/lubing).

Of course that method is pretty much worthless for hunting rifles...leaves the bullet stuck in the bore just about every time you want to remove a cartridge from the chamber without firing it. But, it does work WELL for CBA competition firing from the bench, where you have the opportunity to fire any round in the chamber even after the time limit, with the RO's permission of course.

Dave and the rest using that method almost never discussed it at matches with anyone for a couple of reasons....1) it IS an accuracy edge, and 2) It could be damned dangerous for someone not capable of making/holding components to those tolerances. I guess, "and 3) too", Because he was afraid some foolhardy fella might try it in a jacketed bullet gun and blow his danged face off.

Of course, all this discussion is just on how to get peak accuracy under VERY controlled conditions, not how to make reasonably useable loads for everyday use.

(Hope I got all my math right in there...have lost much of my vision due to a health emergency and don't proof-read very well any more.)
------------------------------


I'm going to recast. I had a small burr that caused finning on the nose, and a little variation between weights.



Yeh, drives me nuts when my moulds start to "peen" a little somewhere or get a little wash between the halves and don't close completely, resulting in that danged finning...\

Good luck on the next casting session.


My country gal's just a moonshiner's daughter, but I love her still.

 
Posts: 9685 | Location: Cave Creek 85331, USA | Registered: 17 August 2001Reply With Quote
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Guys,

I have cases made up that give .0015 clearance for a bullet sized .3095. The throat has a long .310 ball seat so it might be too long for the HBC bullet. I'm getting one of the moulds so I'll be able to try it out. As an after thought my throat taper is 22 1/2 minutes, 45 minutes included, not 22 1/2 degrees. If the thing shows any promise at all I'll follow Lloyds, that is you isn't it Lloyd?, advise and make a case with zero clearance. With a bullet like this it might be the only way to get it to shoot well but even then there's a strong possibility it'll only be at what would be considered low velocity. There's nothing wrong with 1600 fps though if the thing's accurate, even out to 200 yds.

Seeing rifling would be a sure way to see if the nose was expanding but do you think it would at commonly used modern cast bullet load pressures and 20 BNH bullets? Pure lead and black powder is one thing but I don't know if data gathered by it's use is applicable to what we're talking about. I don't know one way or the other and am not trying to be argumentive or pass myself off as another internet expert in any way I'm just thinking out loud.

Pat
 
Posts: 116 | Registered: 27 November 2003Reply With Quote
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AC, Pat -

This has been one of the most in-depth running conversations on step-by-step preparing a cast bullet for highly accurate shooting that I've seen, THANKS much for ALL the input. I'm going to put together the other computer and dig out some bullet and chamber/throat drawings to post.

Have to build some tooling for seating gas checks.

I am concerned about the squareness of the base of the check (perpendicularity with the axis of the bullet), as it also affects group size. Hmmm, wonder if I could use the CMM at work? I may try to square up the base by holding the bullet in a collet in the lathe.


Tim K
(trk)
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Chief of Smoke, Pulaski Coehorn Works & Winery
 
Posts: 621 | Location: Virginia mountains | Registered: 25 December 2002Reply With Quote
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quote:
Originally posted by trk:
AC, Pat -

This has been one of the most in-depth running conversations on step-by-step preparing a cast bullet for highly accurate shooting that I've seen, THANKS much for ALL the input. I'm going to put together the other computer and dig out some bullet and chamber/throat drawings to post.

Have to build some tooling for seating gas checks.

I am concerned about the squareness of the base of the check (perpendicularity with the axis of the bullet), as it also affects group size. Hmmm, wonder if I could use the CMM at work? I may try to square up the base by holding the bullet in a collet in the lathe.


Tim,

It is fun talking about this stuff.

I tried turning the bullet's base a long time ago and it didn't seem to make much of a difference, it fact it didn't make any difference. The best way I've found to seat checks is to modify the ejection pin the way Veral Smith told me to do it. Square up the face of the pin then turn the middle out of it about 1/32 deep until there's a ring about 1/32 or so wide around the edge, none of these measurements are set in stone so just do it so it looks good to you. Anneal the checks and when you get the bullet to the bottom of the stroke give it a little extra bump. There'll be a ring around the edge of the check that as far as I can tell by shooting is pretty square.

I take to this cast bullet stuff pretty laid back and don't go nuts anymore trying to make everything perfect even for the matches. As an example I size my bullets with Lee sizers. With my 6.5 I couldn't get the thing to make it through without totally destroying the check. I tried everything to make it work and finally just started putting a little lube on about every fifth bullet and sizing it without the check. After that I'd seat the check and lube it in an oversized H&I die and then taper it. I realize it's a lot of steps but I don't think many people would agree that you could size a 20 BNH bullet in a Lee die without a check and have it work out alright but it does in fact it might even help make the base a little more square. One thing I do though is to make a new push through pin that more closely fits the die and polish the face good so the bullet has a better chance of aligning itself. The pins that Lee sends along are pretty rough and while I wouldn't swear to it believe that they have a one size fits all per caliber policy

It'd be a little harder to give a bit extra at the bottom with the HBC bullet because of the nose section but it'd be easy to make a hollow top punch and fill it with epoxy to get a good fit and give support.

Id be interested in seeing the HBC print again when you find it.

Pat
 
Posts: 116 | Registered: 27 November 2003Reply With Quote
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quote:
Originally posted by Pat I.:
Guys,

I have cases made up that give .0015 clearance for a bullet sized .3095. The throat has a long .310 ball seat so it might be too long for the HBC bullet. I'm getting one of the moulds so I'll be able to try it out. As an after thought my throat taper is 22 1/2 minutes, 45 minutes included, not 22 1/2 degrees. If the thing shows any promise at all I'll follow Lloyds, that is you isn't it Lloyd?, advise and make a case with zero clearance. With a bullet like this it might be the only way to get it to shoot well but even then there's a strong possibility it'll only be at what would be considered low velocity. There's nothing wrong with 1600 fps though if the thing's accurate, even out to 200 yds.

Seeing rifling would be a sure way to see if the nose was expanding but do you think it would at commonly used modern cast bullet load pressures and 20 BNH bullets? Pure lead and black powder is one thing but I don't know if data gathered by it's use is applicable to what we're talking about. I don't know one way or the other and am not trying to be argumentive or pass myself off as another internet expert in any way I'm just thinking out loud.

Pat


Mr.Ifland (that is you isn't it, Pat?), I really don't know if something like lino will bump up enough to get rifling marks on the nose where there shouldn't be any in theory.

I think it might IF one uses a case full of a medium burning speed powder in the .30-BR...that gives pretty high pressures long enough (comparatively) for cast bullets, to maybe turn the trick.

With heavy enough bullets, so that the inertia is fairly high and the rear of the bullet may begin to move before the nose does, it MIGHT do the trick, but I really have no idea.

Of course, I also don't know if "Dave's approach" will be enough to make HBC bullets shoot as well at short ranges (100 & 200 yards) as the usual bore-riding nose slugs used by many in CBA benchrest. Would be great if they will...would really make for some interesting shooting at longer ranges where the much greater BC would get a chance to come into play.


My country gal's just a moonshiner's daughter, but I love her still.

 
Posts: 9685 | Location: Cave Creek 85331, USA | Registered: 17 August 2001Reply With Quote
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posted Hide Post
quote:
Originally posted by trk:
AC, Pat -

This has been one of the most in-depth running conversations on step-by-step preparing a cast bullet for highly accurate shooting that I've seen, THANKS much for ALL the input. I'm going to put together the other computer and dig out some bullet and chamber/throat drawings to post.

Have to build some tooling for seating gas checks.

I am concerned about the squareness of the base of the check (perpendicularity with the axis of the bullet), as it also affects group size. Hmmm, wonder if I could use the CMM at work? I may try to square up the base by holding the bullet in a collet in the lathe.




That will work. If you have a choice, you might try to adapt a "Rubber-flex" collet of the proper adjustment range...less chance of denting of the bullet by the collet jaws.

Just a reminder, Dave (Lee), Tom (Gray), Mel (Harris), & I all found you can get the EDGES of a bullet base "too square"...that is, too sharp. It is essential to get the horizontal plane of the base 90 degrees to the linear (verticle) plane of the bullet, but we seemed to find it is also critical to keep the edges of those gas checks rounded.

That's another of those little mysteries of cast bullet shooting. None of us found out WHY keeping the edges round rather than sharp made the bullets shoot better. (At least, if one of us did find out why, to my limited knowledge he never told the others.) But, we all noticed they did, when making our independent trips down that path.


My country gal's just a moonshiner's daughter, but I love her still.

 
Posts: 9685 | Location: Cave Creek 85331, USA | Registered: 17 August 2001Reply With Quote
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