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[ARCHIVED THREAD] - Best Twist ratio

Posted: 10/9/2015 9:10:33 PM EDT

I'm looking to start my second AR build and I need help with the twist ratio. I want to build a 18 inch upper that will primarily shoot 55 grain or 62 grain. My last build was a 1-9 twist and that has worked well however finding a 1-9 twist 18 inch barrel that I like can be difficult. I have seen quite a few 1-8 twist barrels. I was wondering how much of a difference that will make, if it will be noticeable or not.

Posted: 10/9/2015 9:14:51 PM EDT

[#1]

I think the 1:8 is preferred over 1:9 twist with 55s.

Posted: 10/9/2015 9:18:29 PM EDT

[#2]

1:8, 1:9, and 1:7 will all shoot 55-62 fine

1:7 and 1:8 will also stabilize 77gr, which is optimum for long range and killing things

Posted: 10/9/2015 9:19:11 PM EDT

[#3]

1:8

Posted: 10/9/2015 9:24:31 PM EDT

[#4]

Actually, 1:9 should be considered better for 55 grain ammo. However, I really find no discernible difference in accuracy whenever I shoot my 55 grain hand loads in either 1:9/1:8 or 1:7. My 3 most recent builds all used 1:8. The following photo is of the first ten shots fired from a FAXON pencil barrel 1:8 twist, 55 grain fioochi soft point. Shots 4-8 were fired after making final scope adjustment.

Posted: 10/9/2015 9:34:26 PM EDT

[#5]

This helps me out a lot I was looking at a FAXON 18 inch 1-8 twist glad to see it has that accuracy with 55 grain thanks!

Posted: 10/9/2015 9:41:20 PM EDT

[#6]

1:7 is best for the heavy and long rounds, 80gr or tracers...1:9 is best with the lighter rounds 40-55gr...1:8 works well with just about anything.

If you can load and feed it from an AR mag, the 1:8 will work fine with it.

That does not mean a 1:7 or 1:9 will not work with most, if not all, common AR rounds...they will, but 1:8 is a good average for anything you're likely to shoot.

Posted: 10/9/2015 10:00:32 PM EDT

[#7]

Quote History

Quoted:
This helps me out a lot I was looking at a FAXON 18 inch 1-8 twist glad to see it has that accuracy with 55 grain thanks!

View Quote

You're probably looking at the same Faxon 18" barrel I'm contemplating for my next build. I hadn't used a FAXON before, but I really like this one, and plan to use another. My current one is the 4150 QPQ material, they generally offer in Stainless QPQ as well, for a bit more money.

Posted: 10/9/2015 11:46:56 PM EDT

[#8]

Hello. Another noob here. I've been reading on this site for a while now and have been feeling this AR obsession slowly creeping over me. I think it is here to stay. I recently completed my first build of an 80 percent lower and rifle kit. I went with the 1:8 barrel for a little different flavor. It is a 20 inch. Have not fired it much yet but I hope it will do well with a little heaver lead.

BTW this is a great site, lots of good info.

Posted: 10/9/2015 11:48:20 PM EDT

[#9]

How much will the extra twist affect velocity?

Posted: 10/10/2015 12:08:24 AM EDT

[#10]

Quote History

Quoted:

How much will the extra twist affect velocity?

View Quote

Very little. I have three identical profile 18" .223 wylde barrels from Green Mountain Rifle barrel. They are in three different twists. 1:14, 1:6 and 1:5. I fired 10 rounds of XM855 from each on the same day over my chronograph to compare velocities. The 1:6 was fastest and I believe that was caused by it having about 400 more rounds through it than the 1:5 or 1:14.

I posted up the individual shot speeds and averages in the GM rifle barrel thread.

Posted: 10/10/2015 11:25:27 AM EDT

[#11]

1:8” is a good all-around choice.

Posted: 10/10/2015 11:10:02 PM EDT

[#12]

All this info has helped so much. Now my dream rifle (one of many) is going to be possible. Thanks all how helped.

[ARCHIVED THREAD] - Best Twist ratio

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