Jump to content


AR15Armory Announcements


Photo

223/556 Twist Rate


  • Please log in to reply
7 replies to this topic

#1 OFFLINE   ehipres

ehipres

  • Group:New Members
  • Member ID: 17,336
  • Posts: 8
  • Joined: Nov. 13 2009
  • Location:Birmingham, Alabama

Posted Nov. 26 2009 - 01:10 AM

I own a Colt Match Target with a 16" barrel. It has a 1:7 twist. I am looking at a new AR, and am curious about the differences in twist. The Ruger and S&W both have a 1:9, while the Colt 6940 has a 1:7. What are some of the other twist rates?

What are the benefits/drawbacks of each? I shoot 55 gr fmj or 55 gr ballistic tips, but I am thinking about a heavier bullet for other applications.

Any help is appreciated.

Eric


#2 OFFLINE   freedomfighter

freedomfighter

    Cornball brother


  • Group:Members
  • Member ID: 17,138
  • Posts: 4,901
  • Joined: Oct. 27 2009
  • Location:Galt's Gulch


Posted Nov. 26 2009 - 01:23 AM

I own a Colt Match Target with a 16" barrel. It has a 1:7 twist. I am looking at a new AR, and am curious about the differences in twist. The Ruger and S&W both have a 1:9, while the Colt 6940 has a 1:7. What are some of the other twist rates?

What are the benefits/drawbacks of each? I shoot 55 gr fmj or 55 gr ballistic tips, but I am thinking about a heavier bullet for other applications.

Any help is appreciated.

Eric

as i understand it, the 1:9 is good for bullet grains up to 62 or 69 but i've heard of people saying heavier shoots fine in their 1:9 so take that for what its worth. if you are wanting to shoot the 75 or 77 grain bullets i would say definitely 1:7. I've read that the 1:7 can overspin lighter bullets causing them to tumble thus hurting accuracy but most of what i've seen is that 55 grainers shoot fine through a 1:7. I suspect that lighter than that, such as 40 or 45 grainers may overspin. basically, 1:9 is good all around except for the super heavy stuff but even then i've heard people say theirs shoots them fine.

hope that clarifies lol :nt:

there are a lot of guys that have more expertise than i but i'd say that unless you are going to shoot superlight bullets that the 1:7 would be best, but if you are going heavier definitely the 1:7


Signature:
Make the first one count...you may not get another.
-...

The longer I work for government...the more I believe we need less of it.
-...

#3 OFFLINE   TomJefferson

TomJefferson

  • Group:Senior Staff
  • Member ID: 7
  • Posts: 28,827
  • Joined: Sep. 13 2005
  • Location:Tennessee


Contributor

Posted Nov. 26 2009 - 02:50 AM

Tell you a very good approach to this question.

Go to Hornady.com and browse their bullets. Notice what twists they recommend and you can even look at the ballistic tables on what they can do. Now you can compare that to what ammo you can get weighing price and availability.

Once you nail down the round you want to shoot most, the twist you need comes pretty easy.

The one standard we have is the most common ammunition available is 55 grain and about all the twists do that just fine out to 300m. That helps. If you are shooting under that range, I'd recommend you rethink your plan making that colt your heavy bullet gun and buy your next one with a slower twist more suited for lighter bullets.

If you plan on shooting over the 300m mark then I'd go for it and look at a 1:8 longer barrel using heavier bullets.

Tj


#4 OFFLINE   TigerStripe

TigerStripe

    The Almighty Bunghole


  • Group:Members
  • Member ID: 384
  • Posts: 42,872
  • Joined: Nov. 13 2005
  • Location:Just this side of Deranged


Contributor

Posted Nov. 27 2009 - 02:20 PM

The supposed disadvantage to the 1:7 twist is decreased barrel life. I haven't had problems shooting 55gr ammo in my 1:7 barrels. 1:9 won't stabilize heavier/longer bullets.

Of the two, I would go with a 1:7 twist. Personally, I would make 1:8 barrels for just about every .223/5.56 AR.



TS


Signature:
There's been a drought in the Moroccan Rain Forest.

WECSOG Certified Armorer

#5 OFFLINE   Swoop

Swoop

  • Group:Members*
  • Member ID: 17,446
  • Posts: 10
  • Joined: Nov. 23 2009
  • Location:Cornelius, OR

Posted Nov. 27 2009 - 09:15 PM

Excellent. Yet another thread that has answered a question for me. If you don't mind I would like to hi-jack this one instead of starting another one for a couple more questions I have pertaining to it please and thank you. :wink:

So with what has been said is it safe to assume that twist is more of a factor depending on the grain being shot? How about a longer range rifle as a opposed to a CQB rifle? Would twist become a factor of those two circumstances or would that relate mostly to barrel length and optics chosen for the specific task at hand? I want to build one of each and I have almost chosen what I want but I am still on the fence about barrel length as well as twist. I am thinking of 16" for the CQB and a 20" or 24" for the longer range AR. How would the different twist and barrel length play a role in these two options?

If someone wouldn't mind clearing this up for me it would be greatly appreciated. Normally I would use the search button but I can't yet, at least for a few more posts anyway. Thanks! :thumb:


#6 OFFLINE   TigerStripe

TigerStripe

    The Almighty Bunghole


  • Group:Members
  • Member ID: 384
  • Posts: 42,872
  • Joined: Nov. 13 2005
  • Location:Just this side of Deranged


Contributor

Posted Nov. 28 2009 - 12:26 AM

Excellent. Yet another thread that has answered a question for me. If you don't mind I would like to hi-jack this one instead of starting another one for a couple more questions I have pertaining to it please and thank you. :wink:

So with what has been said is it safe to assume that twist is more of a factor depending on the grain being shot? How about a longer range rifle as a opposed to a CQB rifle? Would twist become a factor of those two circumstances or would that relate mostly to barrel length and optics chosen for the specific task at hand? I want to build one of each and I have almost chosen what I want but I am still on the fence about barrel length as well as twist. I am thinking of 16" for the CQB and a 20" or 24" for the longer range AR. How would the different twist and barrel length play a role in these two options?

If someone wouldn't mind clearing this up for me it would be greatly appreciated. Normally I would use the search button but I can't yet, at least for a few more posts anyway. Thanks! :thumb:


:welcome: to the Armory! The choice of twist rate is mainly a function of the length or weight of the bullet itself. Barrel length can be taken into account with long distance rifles. With a 14.5 inch or shorter barrel, you will want to stick with a 1:7 barrel to stabilize the bullets, especially the 70 to 77 grain ones.

With an 18 to 20 inch barrel you can easily drop the twist rate to a 1:8 twist. The longer barrel gives the bullet longer to stabilize. A lot of competition guns have an 18 to 20 inch 1:8 stainless barrels. Some people get custom 1:7.75 twists for competition. I wouldn't go past 22 inches on a .223/5.56 barrel because velocity doesn't really increase much past 20 inches.


TS


#7 OFFLINE   Swoop

Swoop

  • Group:Members*
  • Member ID: 17,446
  • Posts: 10
  • Joined: Nov. 23 2009
  • Location:Cornelius, OR

Posted Nov. 28 2009 - 12:55 AM

Thanks for the info TS! That answers my questions.


#8 OFFLINE   TigerStripe

TigerStripe

    The Almighty Bunghole


  • Group:Members
  • Member ID: 384
  • Posts: 42,872
  • Joined: Nov. 13 2005
  • Location:Just this side of Deranged


Contributor

Posted Nov. 28 2009 - 01:08 AM

Thanks for the info TS! That answers my questions.



My pleasure! :thumb:



TS





Forum Statistics

1 user(s) are reading this topic

0 members, 1 guests, 0 anonymous users

Information Center