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12/6/2019 7:27:02 PM
Posted: 10/5/2014 9:38:11 AM EST
[Last Edit: 10/5/2014 9:56:36 AM EST by thompsondd]
What twist rate are you guys getting the best results with?

Thinking of doing a 5.5 to 8.5" 9mm build. I have seen 1:10 and 1:14.

Curious what works best as a general all around twist rate ratio.

I just ordered a complete CMMG 9MM pistol.

It comes with an 8.5" 1:10 twist barrel. http://www.cmmginc.com/product_p/90b3bf0.htm

I was thinking of doing a separate CMMG dedicated 9MM lower with a semi-custom upper build using a Yankee Hill 5.5" barrel. Noticed it comes in a 1:14 twist. http://yhm.net/5-5-9mm-threaded-barrel-without-chrome.html

I realize there is a difference in length between the two so that probably accounts for the need in a difference in twist rate. However, I was wondering what performance differences would be seen between the two as far as accuracy, muzzle velocity, effective range, preferred loads, etc.

Not sure what ammo to run through either. 115gr? 124gr. 147gr? +P? +P+? Will one type of ammo cycle in both?

ETA: I am (fairly) familiar (although not an expert like many here) on the differences in 1:7/1:8/1:9 rifle and carbine barrels for .223/5.56 AR builds. But I have to admit that I have never paid any attention, let alone, learned the difference in twist rates of pistol calibers. Mainly because I never had that option. Could you imagine customizing/changing as much crap on your pistols as you can with your ARs? When I buy pistols, they are what they are. I don't have the option to specify "oh, I want a Glock G17 but I want x length barrel with a 1:n twist rate instead of the factory spec".

Can you imagine the chaos that would ensue if you could 'customize' every gun the way you can with the AR platform? That would be fun (and bank breaking)! However, my pistols are pretty much still the same way the manufacturer made them in their factory. Therefore, I never really paid much attention to what twist rates were and any changes that would come from tinkering with them.

Link Posted: 10/5/2014 10:10:47 AM EST
It is not going to make much difference. Both 1/10 and 1/14 are much faster than necessary, and accuracy would probably be best about with as much as half those rates.

Look at the S&W .357 magnum to see this. I think it is 1/18 3/4", or some thing close to that. This, even though the .357 is very close in diameter to the 9mm, but oftentimes shoots longer bullets. Length of the bullet tells us more than the weight, but with typical handgun bullets length and weight will usually go together.

Handguns, and handgun caliber carbines are mostly shot at close ranges, so no one complains about the over-stabilized bullets.

1/14 would be theoretically slightly better, but it would be a difference hard to actually measure.
Link Posted: 10/5/2014 11:57:48 AM EST
Here is a quick note...

1x10 been std for subgun barrels since WW2,,, common pistol is 1x16,, Berreta 92/M9 is 1x10... 147gr fly just fine from 1x16 or 1x10.

Me,, I prefer common 1x10, that what my Uzi pipe is, and same for my M11-9 barrel I had cut from stainless blank.
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