Dear Members,

I am knew to chat rooms so bear with me. I have some questions that I need some solid advice on from the members. Having hunted with Weatherby rifles my whole life I wanted to stick with that action for my potential project. I would like to convert my .416 Weatherby Magnum to a .500 A-square. I want to use a Pac-nor barrel with a HS precision stock. Even though I am a big bore nut is the .500 A-square going to be substainally more effective than my .460 WM has been on buffalo and elephant? Any advice or suggestions would be appreciated. Thanks.

I would say very much more effective.
Although, with some animals, it makes no difference, as at times some buffalo act like they are on drugs, and pay no mind at the caliber.
You do have the added dia., which is good.
As far as the rifle itself, you may ask someone more informed on the matter here on the forum, such as 500grs.

quote:

Originally posted by WLA:
...is the .500 A-square going to be substainally more effective than my .460 WM has been on buffalo and elephant?

Yes. Be sure to use a 1:10 twist for bullet stabilization. Then push a 600 grain bullet at 2450 fps from the 500 A2 and it will outclass a 460 wby by a wide margin, both due to the greater frontal area of the bullet and due to greater bullet mass.

and we can go about this for daysm as Dan and I totally disagree on the matter. I'll stick with the 500 Nitro, which has NEVER had a want for penetration when loaded to book.

1x18 for pressure reasons, as it can go 1x24 or so... 1x10, from a reloading prespective in a .510 is not a twist, it's a thread. in my opinion, too fast a twist, which barnes made a "line" of (see ackley's books) is the quickest way to ruin a rifle.

jeffe

Glad to see 500grains on the bandwagon for 10" twist.

I have built 2 of the 500A-Square rifles with 10" twist, and found them to be accurate at 1000 yards with 750 grain A-Max bullets at 2150 fps, as well as able to drive a 570 grain GSC FN at 2450 fps to exit on rump to neck shots on 1800 pound bison, repeatably. 600 grainers at 2500 fps are no problem, but not ideal IMHO.

I am also using 10" twist on the 500 Mbogo, and I will use a 10" twist if I ever do a 500 Jeffery.

A-Square uses 10" twist on the 500 A2 rifles they build.

SSK uses 10" twist on the 50 Peacekeeper.

The 50 BMG uses 15" twist, but higher velocities give similar RPS as a 500A2 with 10" twist.

It makes sense: 1:10" twist, and use any bullet you want in the 500A2, and there are so many to choose from.

ah, hmmm,

the 577 nitro, KING of penetration, uses an 18...

http://www.pac-nor.com/barrels/

pacnor sells the majority of their 510 barrels in 1x18... as opposed to their BMG of 1x15 (listed differently)


like being overbore, we will never all agree.. and for a change, i'll stick with nostalgia

quote:

Originally posted by jeffeosso:
ah, hmmm,

the 577 nitro, KING of penetration, uses an 18...

The .577 is the king of penetration?? You were just checking to see if we were asleep, right?

And who cares what Pac-Nor sells the most of. There have been many instances where the majority of mankind has been dead wrong.

Jeffe, are you just in the mood for tonight or what?

RIP
nah, just don't agree on fast twist.

CORRECT twist, certainly, but not over twist.

If you have a copy of ackley's books, look at the barnes QT cartridges... seemed to work, but not for me!!


jeffe

7x57 Mauser---we could ask Bell, if he was still kicking, but he would probably laugh at us for having this discussion about penetration anyway.
But, to the .500 A-2, it should be a good avenue to take.
I've never seen anything hit with one, so
I'm just guessing here. However, I can testify to the .500 3", at 2150fps which has a solid reputation which others can testify to also, and the A-2 is moving along a lot faster, so I don't think it would entirely be a wrong move to make in that direction.

jeff you have a PM

Jeff,

Stabilizing a bullet for punching holes in paper is one thing. Keeping it stable when passing through heavy bone on large animals is another thing.


Also keep in mind that a faster twist is desirable as velocity increases, because as velocity increases so does bullet yaw unless countered by a faster twist.

If you shoot some large game, your views may change.

RIP,

I am a fan of a 1:12" twist.

Listen to Dan, jeffeosso, for he knows of what he speaks.

I used the std 1:15 in my .500a2. Works just fine. Maybe I'll bring it to the STC hunt this year and blow big holes in something.-Rob

Dan,
I guess we all choose what twist we want. On your penetration tests, using the different 470 bullets, what twist was that? IIRC, a 1x18 on a searcy 470, right? Does that invalidate your test results? I don't think it does, at all.

yes, of COURSE twist should change with velocity, which is part of what a good twist calculator will ask for.


Rob,
heh, you might want to rebarrel that low twist to a 1x10!! see you in 2 weeks

jeffe

ScottS,
1:12" twist would be a good one too.
You know if some guys get by with a 1:15" twist on their 500A2's, you are O.K. with a 1:12".

Art Alphin is a smart cookie in all but customer relations and rifle stock design. He chose 1:10" for his 500 A-Square.

J. D. Jones of SSK gave some consideration to twist for the 50 Peacekeeper and came up with the same thing: 1:10".

RIP's ".510/460 Weatherby Improved JAB" is a proven all around performer with bullets from 570 grains to 750 grains, whether penetrating 8 feet of bison with the former or punching paper in the cow pasture at 942 yards with the latter.

quote:

Originally posted by jeffeosso:
On your penetration tests, using the different 470 bullets, what twist was that? IIRC, a 1x18 on a searcy 470, right?

No.

Jeffe- Got the barrel in the vise right now! Got a BIG long Cheater bar and some real good vise grips on it! I'm gonna go for 1:12 or so! Wheres my string twist measuring gizmo! Whoo-We I just KNOW it will work better that way! Gotta get me more penetration!!!-Rob

Better to have too much twist than not enough.
Also, I have seen some tests where with soft and hollow point bullets, a faster twist gave more expansion.

So with a solid, better stabilitation, with a soft more expansion....
Is that a win-win situation?


I do know this... When you go to pull the cork out of a bottle of Single Malt Scotch, the faster you "twist it" the easier it comes out.

quote:

Better to have too much twist than not enough.

Doesn't a faster twist create higher pressures?

quote:

Originally posted by JMJ888:

quote:

Better to have too much twist than not enough.

Doesn't a faster twist create higher pressures?

Well said, NE 450 No2.

JMJ888,
Having a bit of experience with the 404 Jeffery, 470 Capstick and 500 A-Square, all with 1:10" twist, I can tell you this: any pressure increase with a faster twist of only 1:10" is trivial, negligible, not a worry.

Look at the pressure data in the A-Square manual, tested with a 1:10" twist 500 A-Square, BTW.

No problem.

Rip,
and my $1400 experiement shows clearly that pressure increases, DRAMTICALLY with twist.

1x16, x12, and x10 358 winchesters..

max load in the 1x10 is about 22fps slower in the 12, and ~60fps slower in the x16...

very warm/hot loads in the x16 are CRITICALLY over pressure (splattered flattened primers) in the 1x10..

So, I built all my loads for the 1x10, and it's FINE in the x12 and x16..

Faster twist ALWAYS results in more pressure, aabe, which sometimes results in more velocity.

As with all things, moderation is generally a safe route.

1x10 is FINE in a 338 or less, rather much in a 358, and not the best possible path in the over 40 calibers, imnsho.


jeffe

fast(er) twist = increased rotational torque on bullet = increased chances of bullet yawing in flight = increase in the timeline between exiting the barel and stabilizing = more radial/axial movement. The govt spent millions of our $$$ proving that you can, in fact, over spin a projectile.
Look at the Picatinny Arsenal Study. The faster you spin a projectile, the more you torque it. Enough torque, add the difference between geometric and actual center of gravity and the projectile flies apart.

JMHO...and the arsenal's.

Rich

In all seriousness, I doubt a 1:10 twist buys you anything over 1:15 in the 500a2. The major selling point of the 500a2 in my opinion is the ability to shoot .50BMG military bullets or A-max's for Ha ha's. .50 Peacekeeper, WOW what a NEW concept! That Art Alpin sure is a smart guy( just ask the feds). The 1:15 gives much better results at lower pressures with these bullets.
Finally, I've observed the same increase in pressure with faster twist rates that Jeffe has. Not particularily surprising, but not a good thing either. In addition depending on the bullets construction, they can and do come appart with fast twist barrels due to the higher torque figures. Of course Muzzel brakes become more effective as the pressure rises, so that may offset the disadvantage. You do use muzzel brakes on your 500a2's don't you?-Rob

Well this thread has gotten interesting. A 1:10" twist versus a 1:15" twist and pressure. The twist differential will definitely increase the torque load on the barrel by almost exactly 5%. This differential in force distribution through the barrel will also apply to pressure, so a 1:10" twist should experience an ~ 5% increase in pressure relative to a 1:15" twist. So what, you reduce your load a bit. Big deal.

The military may well have learned that you can overstabilize a bullet in AIR, but believe me a 1:12" does a better job in an animals innards than the 1:18". I cannot comment on a 1:15" as I haven't shot anything with a 50 BMG outside of some paper and a few rocks. I also cannot comment directly on Ron's 1:10" twist, but my rifles are 1:12" and they will shoot better than 1.5 MOA and typically around 1 MOA. Not bad for so-called "elephant" guns.

Haven't had any issues with bullets exploding in flight due to over rotation (let alone in animals which are typically a tad tougher on bullets than air). Probably because your typical 50 caliber elephant gun bullet has a much stronger jacket than you typical .224 varmit bullet, as well as lower rotational speed (do I have to do the math for you guys there too, or can you do it?).

quote:

Originally posted by N E 450 No2:
Better to have too much twist than not enough.
Also, I have seen some tests where with soft and hollow point bullets, a faster twist gave more expansion.

So with a solid, better stabilitation, with a soft more expansion....
Is that a win-win situation?


I do know this... When you go to pull the cork out of a bottle of Single Malt Scotch, the faster you "twist it" the easier it comes out.

My .500a2 will go 2700fps at around 65Kpsi with a 500 gr woodleigh solid with a 1:15 twist. Its running near 65Kpsi. With a 1:10 twist at the same velocity, you'll be overpressure and the belts will expand to the point the primers fall out. This is not a good thing! Whats the point of loading the 500a2 down? It's purpose is maximum clobber factor!-Rob

quote:

Stabilizing a bullet for punching holes in paper is one thing. Keeping it stable when passing through heavy bone on large animals is another thing

I would think that as long as a bullet punches a round hole (not hitting sideways) with acceptable accuracy through paper then the bullet is stabilized in a manner to produce sufficient penetration.

quote:

The twist differential will definitely increase the torque load on the barrel by almost exactly 5%. This differential in force distribution through the barrel will also apply to pressure, so a 1:10" twist should experience an ~ 5% increase in pressure relative to a 1:15" twist. So what, you reduce your load a bit. Big deal.

So you reduce your load to compensate for the faster twist...wouldn't that reduce your overall velocity / momentum / penetration? Seems logical that a slower twist (with stabilized projectile) pushed to higher velocities would offer greater penetration than the converse.

Rogunbuilder,

quote:

My .500a2 will go 2700fps at around 65Kpsi with a 500 gr woodleigh solid with a 1:15 twist. Its running near 65Kpsi. With a 1:10 twist at the same velocity, you'll be overpressure and the belts will expand to the point the primers fall out.

Couple of questions/points.

1.) When did Woodleigh start making 0.510" diameter solids weighing 500 grains?

2.) The chamber pressure required to blow a primer in a 460 Weatherby case is WELL over 90,000 psi! The twist differential you provide WOULD NOT raise pressure from 65 ksi to that level, sorry to break it to you.

JMJ888,

Jeffeosso has spoken to the velocity vs twist issue already in this thread. I quote:

quote:

max load in the 1x10 is about 22fps slower in the 12, and ~60fps slower in the x16...

The pressure causes the velocity. The higher twist rate is said to produce the same pressure with a smaller powder charge. The same is said of "tight" vs "loose" barrels/chambers.

Heck shoot whatever you want, but please don't bitch about what I am shooting or RIP for that matter.

Later

Thanks all, especially ScottS for the math.

I sure am glad I have to compress my powder less when I am using the 1:10" twist to get pressures and velocities where I want to be.

50 to 60 Kpsi will do all I want with any of the 570 to 750 grainers.

Rotational energy and momentum are such a tiny fraction of the total linear KE and momentum, it is trivial. Do the math.

quote:

Jeffeosso has spoken to the velocity vs twist issue already in this thread. I quote:

quote:
max load in the 1x10 is about 22fps slower in the 12, and ~60fps slower in the x16...

His point being that a max load at say 65k in a 10 twist barrel will a bit slower in a 12 or 15 and lower pressure. Conversely, a 65K load in the 12 or 15 twist will be well over 65K in the faster 10 twist. Since you did the math I will just use that:

quote:

This differential in force distribution through the barrel will also apply to pressure, so a 1:10" twist should experience an ~ 5% increase in pressure relative to a 1:15" twist. So what, you reduce your load a bit.

My point being that overstabilization provides unecessary pressure when a 1 in 12 or 15 will work just fine. Rip said so himself:

quote:

ScottS,
1:12" twist would be a good one too.
You know if some guys get by with a 1:15" twist on their 500A2's, you are O.K. with a 1:12".

Now if you are going to stabilze a 750 AMAX which is as long as my arm then 1 in 10 makes sense but for bullets weights from 535-700gr its not necessary for better penetration.

Here is some food for thought from the AR reloading page:

quote:

The following data was developed by my friend Mitch Carter, in a custom rifle built on a Weatherby Mk V action. It originally was a 460 Weatherby. This rifle had a 26" McGowan barrel, with a 1 in 12 twist, and a muzzle brake was also installed by McGowan. Mitch noted that this rifle is more accurate with the 700 grain bullets than the 600, which might be due to the fast twist barrel.

JMJ888,

I suggest you brush up on your reading comprehension skills. Jeffeosso said: that the load he used in a 1:10" twist barrel was 22 fps slower in his 1:12" barrel and ~ 60 fps in his 1:16" barrel.

Here if you have a sloppy chamber and a oversized bore and develop a max load in that rifle then shoot it in a tight match chamber tight bored rifle what do you think would happen.

The answer is that the tight chambered tight bored rifle would shoot faster and at higher pressure. This is the theory behind the faster twist. I say theory because it hasn't been proven to me. There are many many variables at work.

Like I said before you don't like how I set up my CUSTOM rifles so be it, go build your own. The important thing kids is to have safe recreational fun.

quote:

I suggest you brush up on your reading comprehension skills.

Read the rest of that quote that Jeffe posted...here it is again:

quote:

max load in the 1x10 is about 22fps slower in the 12, and ~60fps slower in the x16...

very warm/hot loads in the x16 are CRITICALLY over pressure (splattered flattened primers) in the 1x10..

Whole point...not half.

quote:

Here if you have a sloppy chamber and a oversized bore and develop a max load in that rifle then shoot it in a tight match chamber tight bored rifle what do you think would happen.

I have heard of a tight chambers and "tight benchrest necks" but I was unaware they changed bore sizes. My understanding was that you put a .510 diameter bullet down a .510 diameter tube...458 down a .458 tube.

quote:

There are many many variables at work.

Kind of like your arguments. Point is the twist rate...benchrest and match chambers is adding additional information not relevant to the discussion.

quote:

The important thing kids is to have safe recreational fun.

I couldn't agree more but then again I like operating within reasonable pressure guidelines.

quote:

The chamber pressure required to blow a primer in a 460 Weatherby case is WELL over 90,000 psi!

Not sure what kind of primers you use but I am pretty sure primers will go sooner than that. Pipe bomb anyone?

quote:

Originally posted by ScottS:
2.) The chamber pressure required to blow a primer in a 460 Weatherby case is WELL over 90,000 psi!

Scott,
WELL over 90kpsi?
Scott, what's your case life 0.8 reloads?



90kspi?



Amazing....


jeffe

Just a thought(with no experience), so don't clobber me if it's a bad idea, but has anyone tryed a variable twist rate where it starts with a slower twist rate & goes to a faster twist rate by the time it gets to the end of the barrel?

gain twist barrels were very popular (and effective) with black powder, and smokeless ...with lead bullets. The idea was that the gradually increasing twist would help increase the gas seal in the bore. Jacketed bullets do not seem to benefit from it.

Rich

ScottS- Sorry but your going back to your old self again aren't you. Meds wear off to quickly? Since when do you have any REAL experience with the .460 WBY? 90KPSI to blow primers? Do I need to teach you again about pressure measurements? You need to check the expiration date on your lithium! Try again!. Do the math then buy the gun!-Rob

I AM NOT!! defending ScottS (he's a big boy and can handle that himself) but I have seen .001-.003" variance in 45 and 50 caliber rifle barrels. A load worked up in a "loose" barrel might be a bit warm-ish in a "tight" one. A friend bought two Lilja barrels in 6mm for a Wyoming Prairie Dog LR rifle. There was 200fps difference in those two barrels (screwed on the same action/stock) with ammunition from the same box. I chronographed them. He sent both barrels back to Dan after PD season was over, and Dan could NOT find .001" difference anywhere in those two 28" x 1.25" barrels. Fifteen years later, he still has absolutely Zero idea why. He did replace the barrel.

Rich

Rich,
yep, there's extreme cases of fast and slow barrels. Sure enough... but I am certain YOU aren't damn fool enough to take the hottest load you have from one barrel and go stick it in a TOTALLY unknown barrel.

This is a common distractor of a troll, that they hunt every thing under the sun to shift focus, to pretty soon he'll be talking about primers impacting variable barrels, and case weight, vs barrel length, and no longer talking about TWIST.

jeffe

Just so everybody here understands the facts and History. ScottS (Scott Sweet) is a major Troll on this site. He first appeared years ago as ToddE, became Axel , Assclown( I gave him that name and the idiot liked it and adopted it) you can guess why and a ton of other names I can't even remember. He gives himself away by quoting pseudo science and engineering data, that in the end is scientifically flawed and generally a lie. He apparantly may have briefly ( right Scott) owned one real big bore rifle a .500 AHR in his career and probably nothing else. He makes up load data and what he actually knows about big bores he learned on this site and from his extensive googling skills. He may in fact work as a low level quality assurance auditor at a well known detroit automaker or subsidiary. HE HAS SERIOUS MENTAL PROBLEMS AND FORGETS OR DECEIDES NOT TO TAKE HIS MEDS. Scott apparantly dislikes us because we actually shoot and own the very guns he dreams of and have the audacity to talk about them. Make no mistake, ScottS is a jerk and should not be believed by anyone. I truly feel sorry for him. He wants despareately to be seen as an important member of this site and his continuous failure devastaes him. he disappeared from the site for about a year in the hopes that no one whould be left who remembers him. Sorry Scott! AR Reader be advised! Check with the moderator if you think I'm overstating the facts.-Rob