Twist rate

Talk about the AR15 style rifles chambered in 450 Bushmaster.

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Twist rate

Postby cowboybart » Fri Aug 18, 2017 7:31 pm

New here.
I am curious, how heavy of a bullet will a 24" twist stabilize? I am wanting to shoot 360gr bullets and want to know if they will stabilize. Will 24" twist stabilize a 400 gr bullet??
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Re: Twist rate

Postby Texas Sheepdawg » Fri Aug 18, 2017 7:57 pm

I believe Tim says the 1:24 will do okay to 325 grain. Not too sure about 350+ though. But they make barrels these days with 1:16 rates so shop around. I know the 300 grain bullets fly fine in the 1:24.
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Re: Twist rate

Postby Bmt85 » Sat Aug 19, 2017 12:54 pm

Well, playing with a twist rate calculator, a 1:24 twist should be able to handle around a 400gr jacketed, and 300gr monolithic copper (except a 300gr TTSX, it will be too long to properly stabilize). Of course thats looking at resized .458 bullets, and bullet length has a lot to do with it. Another thing to think about, the shorter bullets in those weight classes will have a better chance to stabilize, however they will also have a more blunt nose profile. That means that your O.A.L. will be shorter, which leads to less powder, and less energy.

My personal opinion is stick to 350gr or less for jacketed, and a 275 XPB or TSX in a 1:24 twist, for the sake of getting the most energy out of your platform.
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Re: Twist rate

Postby cowboybart » Mon Aug 21, 2017 8:25 pm

I want to use this for the ever growing Grizzly problem that Wash DC has placed at my doorstep. My mold for my 454 throws them at 362grs. My wife can't handle the recoil of a 454, so that is out. I believe a handgun is only good to fight your way to a rifle.
When I take my dogs out to do their business, I currently take a 356 Win with 285gr bullets out with me. My wife can handle this, and I consider this minimum for a grizzly that wants to chew on me. I was thinking that a 450BM with the same 360gr bullet would be good bear medicine. I will powder coat them to keep the gas system clean and would like a left side charging upper. Most of the time I will plink with 230 FMJ bullets, but when it comes to business, I want the heaviest bullets I can stuff in the case. I am really not interested in swaging 400 or 500gr 458 bullets down and feel that a 360gr cast bullet will penetrate enough to make a grizzly reconsider his options. 12 rounds, delivering 10oz of lead, in a reliable auto loader, makes me more comfortable than 6 rounds, from a lever action, delivering 4 oz of lead.

If a 24" twist will do it, I am OK with that. If not, I'll look for a 20" twist.
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Re: Twist rate

Postby cowboybart » Mon Aug 21, 2017 8:56 pm

My 360gr bullets measures .835" long. The bearing surface is about .7".
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Re: Twist rate

Postby Texas Sheepdawg » Mon Aug 21, 2017 9:35 pm

cowboybart wrote:My 360gr bullets measures .835" long. The bearing surface is about .7".


We have a member up in alaska who's used 300 grain deep curls (Speer) and whomping those bears up there..... he posted a story here on the trophy room back around four years ago.
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Re: Twist rate

Postby Bmt85 » Tue Aug 22, 2017 1:45 am

You should have no issue stabilizing that bullet in a 1:24 twist. I would look at 1680 powder for load development.
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Re: Twist rate

Postby Texas Sheepdawg » Tue Aug 22, 2017 8:26 am

cowboybart wrote:I want to use this for the ever growing Grizzly problem that Wash DC has placed at my doorstep. My mold for my 454 throws them at 362grs. My wife can't handle the recoil of a 454, so that is out. I believe a handgun is only good to fight your way to a rifle.
When I take my dogs out to do their business, I currently take a 356 Win with 285gr bullets out with me. My wife can handle this, and I consider this minimum for a grizzly that wants to chew on me. I was thinking that a 450BM with the same 360gr bullet would be good bear medicine. I will powder coat them to keep the gas system clean and would like a left side charging upper. Most of the time I will plink with 230 FMJ bullets, but when it comes to business, I want the heaviest bullets I can stuff in the case. I am really not interested in swaging 400 or 500gr 458 bullets down and feel that a 360gr cast bullet will penetrate enough to make a grizzly reconsider his options. 12 rounds, delivering 10oz of lead, in a reliable auto loader, makes me more comfortable than 6 rounds, from a lever action, delivering 4 oz of lead.

If a 24" twist will do it, I am OK with that. If not, I'll look for a 20" twist.


Please go read this post.
viewtopic.php?f=13&t=12715
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Re: Twist rate

Postby mcb » Tue Aug 22, 2017 11:33 am

I resized some Remington 405gr SP down to .452 and fired them from my 20 inch 1: 24 twist 450 Bushmaster at 1050fps and they punched nice round holes at 100 yards.

Image

This is a good bullet stabilizer calculator. Enter you bullet data and muzzle velocity and some atmosphere condition and it will tell you if you have a stable bullet.

http://www.bergerbullets.com/twist-rate-calculator/
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Re: Twist rate

Postby cowboybart » Wed Aug 23, 2017 7:31 am

Texas Sheepdawg wrote:
Please go read this post.
viewtopic.php?f=13&t=12715


That's a good read. BIG bear at 1300 lb!!! Not to take anything away from the load, shooter or bear, but my situation is slightly different. While the bears here go 600-800 lbs, most are in the 650 range (half of the weight of the bear in the thread), the one I might have to shoot at will be coming at me with all of hell's fury. Animals are easier to kill if they don't know your there. If they are full of adrenaline, it takes more to stop them. Given the performance of the above load and the penetration thru a lot of bear, I think a 300 gr bullet will make me sleep OK. I am a heavy bullet kind of guy, rather than a velocity person.
Thanx for all the tips, now to go out and find the parts for the build.
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