Rifleing twist?

**seanmunger** · 27 April 2009, 03:23

I have been doing some reading on this forum and others, as well as every book i can find. you guys seep to big supporters of a 1 in 7 twist in your carbines... i was wondering why? everything i have read says that is too fast, that it will spin the jacket off lighter loads.
maybe i have my facts wrong, but i would apreciate any insight you guys have.

**rob_s** · 27 April 2009, 04:44

What do you consider "lighter loads"?

I was shooting two 1:7 carbines at the range yesterday, and put loads varying from 55 grains soft point, 55 grain XM193, 62 grain FMJ, 75 grain HP, and 75 grain Black Hills.

Barrel twist selection comes down to application (mission drives the gear train, as Pat Rogers says). The more effective 5.56 loads are in the 75-77 grain range, and I buy my ARs with an eye towards home defense and hunting hogs. Yes, I typically shoot way more 55 or 62 grain ammo, but I choose my rifling twist (and all my gear, actually) based on what I consider "critical use", so 75-77 grain are it, and as such 1:7 is what I buy. Happily it works just fine all the way down to 55 grain surplus ammo.

**TehLlama** · 28 April 2009, 17:12

Likewise - I based my choice on Rob's advice - when I care about incremental accuracy, I'm shooting 75-77gr, and when I'm running bulk 55gr through a rifle/carbine, then any sub-2MOA accuracy is acceptable.
Even though I have limited need for 1:7, it fit what I needed best: optimal performance with my 75gr Match and FPD rounds, and works with cheap bulk 55gr.

**Stickman** · 28 April 2009, 17:54

Originally Posted by seanmunger

I have been doing some reading on this forum and others, as well as every book i can find. you guys seep to big supporters of a 1 in 7 twist in your carbines... i was wondering why? everything i have read says that is too fast, that it will spin the jacket off lighter loads.
maybe i have my facts wrong, but i would apreciate any insight you guys have.

If you are shooting the real light varmit loads in the 45grain range, you may want to stay with a more shallow twist, especially if you are shooting for max accuracy.

If you are shooting 55 grain and higher, the 1/7 works well.

If you are shooting 55-68 grain, and have zero plans to ever go heavier, a 1/9 twist will do well for you.

**seanmunger** · 30 April 2009, 20:42

thanks guys, you helped a lot. i just bought a S&W M&P15 with a 1/9 twist.

**Ryo** · 30 April 2009, 22:52

1/9 twist is very good too

**cmoore** · 29 June 2009, 01:50

The 1/7 is very versatile like rob_s said. You can pump 55 thru 75 grain without any issues. We have both M4's and M16A1's at work. M4's 1/7 will handle the 62 grain M855 without a problem, the M16's 1/12 will not (accurately). The 1/12 causes the 62 to "keyhole", or tumble into, a target @ 100 yards.

Hope this helps you out...

cmoore...

out...

**federalist22** · 29 June 2009, 03:58

While lighter loads (40ish grain) are cheaper than the standard stuff you find, the 1/12 twist is good for them, but you need a long barrel (20"-24") to stabilize the round. Accuracy and extended range with a 1/12 can be excellent for 40gr/45gr varmint loads. My rifles are all either 1:8 or 1:9, so I shoot anything from 55gr for short range target, plinking, etc. in the 1:8 or 1:9, but 68gr and 75gr for longer range shooting in the 1:8.

**Paulo_Santos** · 30 June 2009, 02:47

I still don't understand why the 1:8" twist isn't the standard twist. Sure, for the MIlitary, I undersdtand why they need the 1:7" twist, but for civilian/LE use, the 1:8" can shoot evrything from 40-80 GR.

**AR Performance** · 30 June 2009, 23:21

Originally Posted by paulosantos

I still don't understand why the 1:8" twist isn't the standard twist. Sure, for the MIlitary, I undersdtand why they need the 1:7" twist, but for civilian/LE use, the 1:8" can shoot evrything from 40-80 GR.

I like 8 twist myself, polygonal rifling.
chromed or Nitrided?

**Ryo** · 1 July 2009, 01:06

I prefer the 1:8 twist myself.

**Cameron** · 1 July 2009, 09:36

I have both 1in7 and 1in9 and I really think that the 1in9 makes a lot of sense for the civilian American shooter. Being able to use 40-70gr makes ammo sourcing very easy.

Cameron

**NickDrak** · 2 July 2009, 02:02

1/7, 1/8 & 1/9 are all acceptable in the AR platform for taking care of serious business.

Additionally, some of the most effective loads are also in the 62-64gr class, and every 1/9 twist barrel I have ever seen has handled the 62-64gr. loads very well.

**rob_s** · 2 July 2009, 02:53

I don't recall ever having fired anything under 55 grain in one of my ARs. I also don't recall having ever seen any .223 ammo under 55 grain that would be remotely cost effective to shoot in an AR the way that I shoot. I suppose if it came down to a choice between not shooting anymore and shooting $30/box varmint loads I would... no, scratch that, I'd shoot the 9mm or the .22 thanks.

I think that the 1:9 was a perhaps suited to the industry 20 years ago when manufacturers were looking to provide a twist that would shoot the XM193 and Q3131A that was everywhere as well as the commercial loads that were typical in .223 that tended to the lighter side, but in today's market and with the more dynamic types of shooting and better availability of more ammo (recent price spikes and shortages notwithstanding) I think it's kind of anachronistic. Everyone talks about 1:9, and even 1:8, working for the lighter loads, but frankly I don't care and I don't think anyone else does either. 55-77 is where the market is today IMHO and that's where the 1:7 shines. Christ, WOLF of all companies makes a 75 grain now! 1:8 is fine if that's what blows your skirt up but I see no point in making a big deal out of it, or what it would offer in terms of practicality that 1:7 isn't.

**5pins** · 2 July 2009, 09:32

When the rifles with 1/7 starting to hit the market in the late 80’s there was a lot of talk about the lighter 55gr bullets causing throat erosion. I don’t know how true the rumors were but I remember reading about it a lot. Funny how we don’t hear about that problem now.

Also some felt that the 1/7 twist didn’t provide the best accuracy with the 55gr bullets, the most common at the time. I think the shooting industry responded by going to the slower 1/9 with the claim of better accuracy and longer barrel life.

It wasn’t until high power shooters started using heaver match bullets that people started to see the usefulness of a faster twist. Later the military started using the heaver stuff for better performance at longer ranges. The trend started coming back to the faster 1/7 when it was discovered how well the heaver OTM bullets performed in combat.

I have shot bullets down to 45gr in with the 1/7 with no problems.

Here is a video of a 1/7 shooting 35gr and 40gr bullets. You will notice that the 35gr bullets are disintegrating in flight a few feet away after being shot. The 40gr are doing fine at 300 yards.

http://www.youtube.com/watch?v=GTJaN...e=channel_page

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