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-   -   Handgun Barrel Twist-Rate Article (http://glocktalk.com/forums/showthread.php?t=1456639)

greenlion 12-08-2012 10:10

Handgun Barrel Twist-Rate Article
 
For those of you who just picked up (or will) the new issue of Handguns magazine, there is an interesting article about bullet stability after penetrating barriers, using different barrel twist rates. (Twist and Shout: by Dick Metcalf) I won't spoil the article for those who have not read it, but if you have already, you will probably be wondering what the twist rates are for GLOCK barrels.

Here ya go..

For all 9mm, 10mm, .357, and .40 caliber pistol lines, the twist rate is - One in 9.84 in.

For the .45ACP and .45GAP lines, the twist is - One in 15.74 in.

SJ 40 12-08-2012 14:26

I'll be interested to read it. I know that the Wilson barrel that I have for a G 22 that is 1/16" at 25 yards is not greatly more or less accurate than a factory barrel. SJ 40

.38 super 12-09-2012 01:03

Pistol bullets does not need much stabilization compared to rifle bullets where the center of gravity is close to the tail of the bullet rather than the front part... On the other hand the faster the bullets spins, the better penetration is...

I will get the magazine, because it is interesting to read the article, but with all my respect to Mr Metcalf, some 3-4 years ago he wrote that on S&W, M&P when you pull the trigger it additionally loads the striker before release it, which is incorrect, M&P's striker is fully loaded by the cycle of the gun... I did send him an a nice e-mail asking about it, stating a video by AGA where you can clearly see that striker does not go back when the trigger is pulled but did not have any respond... Not like I was expecting one... It wasn't very important anyway...

greenlion 12-09-2012 07:29

Quote:

Originally Posted by .38 super (Post 19715418)
Pistol bullets does not need much stabilization compared to rifle bullets where the center of gravity is close to the tail of the bullet rather than the front part... On the other hand the faster the bullets spins, the better penetration is...

That is the interesting bit in the article though. It shows what happens to bullets spinning with a faster twist rate AFTER they penetrate the barrier. He also tells how slow motion cameras have revealed bullets doing much more than they should be doing during regular flight, when the twist is too slow.

He says that, based on new evidence, many manufacturers in the industry are changing their minds about what you stated in your post, and going with a faster twist rate for pistol bullets.

SJ 40 12-09-2012 10:46

It will be interesting to see if the Greenhill formula gets redone or replaced at least when it comes to handguns. SJ 40

.38 super 12-09-2012 14:54

Quote:

Originally Posted by greenlion (Post 19715743)
That is the interesting bit in the article though. It shows what happens to bullets spinning with a faster twist rate AFTER they penetrate the barrier. He also tells how slow motion cameras have revealed bullets doing much more than they should be doing during regular flight, when the twist is too slow.

He says that, based on new evidence, many manufacturers in the industry are changing their minds about what you stated in your post, and going with a faster twist rate for pistol bullets.

This will be interesting article and I'll pick up the magazine tonight... Actually this is well known fact in rifle bullets - for example, 7.62 AK round comes out of 1:10 twist rate barrel, where 5.56 AR round comes out of 1:7 barrel twist ( very generally speaking...) Even the AK round is heavier and brakes bricks and such barrier material, it will not compare at any way to the AR round that drills trough steel plates way easier... One of the reasons is - it is more stabilized... Of course this is very raw example - AK round is intermediate cartridge and 5.56 is a rifle cartridge but you got the idea...
a simple, hot loaded FMJ 9x19 will easily penetrate 16" FBI protocol, gelatin block, even out of 4" barrel, but I don't understand who will need such round unless we are talking some special purposes guns and ammo...

jeremy1 12-09-2012 18:54

I didn't read the article, but have read PO Ackley's books, and this is nothing new. he experimented with twist rates extensively, and claimed that the RPM is more important that muzzle energy when penetrating. In one test he shot 1/2 " armour plate with a 30.06, 270, and 220 swift. The Swift was the only round to penetrate even though the muzzle energy was considerably less.

The theory is sound, but the question is what do you need to penetrate with a hand gun?

.38 super 12-09-2012 19:31

Which one is about twist rate experiments, if you can point it to me ? I am curious to look at it, TIA.

jeremy1 12-09-2012 21:30

Quote:

Originally Posted by .38 super (Post 19718062)
Which one is about twist rate experiments, if you can point it to me ? I am curious to look at it, TIA.

I went looking and it is in Handbook for Shooters and Relaoders Volume 1 Page 81. This is in the killing power and there are pics of the armour plate that was shot at with the 30.06, 270, and 220 swift.

I did read another article from an old reloading magazine a friend had, but I dont have access to it.

His books are excellent and a must read for reloaders.

.38 super 12-09-2012 22:50

Quote:

Originally Posted by jeremy1 (Post 19718483)
I went looking and it is in Handbook for Shooters and Relaoders Volume 1 Page 81. This is in the killing power and there are pics of the armor plate that was shot at with the 30.06, 270, and 220 swift.

I did read another article from an old reloading magazine a friend had, but I dont have access to it.

His books are excellent and a must read for reloaders.

I'll look it up, thank you. I found some of the books in Amazon, one of them was like $170+, I'll go check the volume you mention, hopefully it isn't terribly expensive...

rimshaker 12-09-2012 23:35

Twist rates and bullet stability are also very important when it comes to using silencers. Last thing you want is the bullet touching anything.

Glock and HK barrels use the same 1:9.84" rifling and Sig uses 1:10". Most aftermarket barrels use the slower 1:16" rifling. So basically stick with OEM factory barrels.

jeremy1 12-10-2012 13:41

Quote:

Originally Posted by .38 super (Post 19718746)
I'll look it up, thank you. I found some of the books in Amazon, one of them was like $170+, I'll go check the volume you mention, hopefully it isn't terribly expensive...

They are hard to find. I have to return them to the guy who lent them to me. He is asking. I have been looking for a set, but no luck.


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