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9/22/2017 12:11:25 AM
Posted: 9/22/2002 8:53:43 AM EDT
I was looking on the RRA site and on their 24 inch varmint barrel they have a 1:12 twist option. Is this better than 1:8? What do the different twist rates allow you to do ammuintion wise? which would you prefer? and any other comments or advice would be appreciated.
Link Posted: 9/22/2002 10:11:40 AM EDT
[Last Edit: 9/22/2002 10:19:28 AM EDT by gcmj45acp]
Read the info at www.ammo-oracle.com. I learned a lot. If you are going for longer bullets(these also tend to be heavier 69-80grain bullets) then a faster twist is better. If you are going for shorter bullets, especially those weighing less than 50 grains, a slower twist is normally just fine but faster twists normally won't hurt. You can however, eventually get to a point where the tight twist is bad and you actually over spin the bullet resulting in a bullet that remains nose high through it's entire flight path. There are also rare instances where the super light 50gr and lighter, hollowpoint and frangible bullets don't make it down range intact when fired from tight 1:7 and 1:8 twist barrels at high velocities. Another thing of note is that the tighter twist barrels do wear more assuming all things are equal. However, the average shooter will never shoot their rifle enough to notice the difference in barrel life unless they shoot full-auto a lot.

I'm not a varminter but from my expanding experience in long range shooting with my AR's I am learning that as you get past 300m, you often have to get into progressively heavier bullets that are longer and require tighter twist rates to remain stable in flight. I haven't tried 1000m yet and probably won't with the 5.56mm but at 500-600m, I am getting into the 75gr Hornady's and have found that my 16" and 20", 1:9 twist, Bushmasters don't let that bullet remain stable at that distance. It's just fine however back at 300m and the 16" Bushsy actually out shoots some 20" 1:7 rifles I've seen. My 1:7, Colt Sporter Target on the other hand is shooting eight to ten inch groups at 600m with no "key holes" if I do my part. The only thing that has been done to the Sporter Target is the addition of a freefloat tube under the handguards. If I decide I really am going to get back into DCM, this will be my first 5.56 rifle for the sport after having "retired" from shooting an M1A to start college almost ten years ago.
Link Posted: 9/23/2002 5:31:50 AM EDT
so for a 62 or 63 grain bullet on a 24 inch barrel would you rather have 1:8 or 1:12
Link Posted: 9/23/2002 5:50:04 AM EDT
[Last Edit: 9/23/2002 5:52:53 AM EDT by Quarterbore]
For the 62-gr weight I would rather have the 1:8 twist....

You were given very good advise and I like to think of the 1:12 twist as being ideal for bullets upto 55-gr. The 1:9 twist is probably the best all around twist while the 1:8 is better for the heavier bullets.

Just the same, if you use a 24-inch barrel with 1:8 twist you will have great accuracy plus you will later be able to shoot the 69-gr and heavier VLD bullets that will really make your AR-15 a long range weapon. The 1:12 barrel will NOT work with these bullets!

Now, if you wanted to use 40-gr Nosler Ballistic tips, then you would want the 1:12 twist as I am not sure the little BTs will stand up to the stress of the 1:8 barrel! I know I had some problems with my 1:7 twist Colt HBAR barrel and I switched to a 1:9 twist Bushmaster HBAR that seemed to solve the problem... Even this is a little fast for these bullets however as they were exploding on contact (even if the contact was a paper target!).

Good Luck
Link Posted: 9/23/2002 5:53:53 AM EDT
1:12 is only good for light bullets. Its best for 40 and 45gr by my experience. The 1:8 is much more versatile since it will handle anything from 40-75gr. Don't waste your money on the 1:12, you'll regret it later.
Link Posted: 9/23/2002 1:45:04 PM EDT
Barrel length won't have anything to do with the twist you select. Bullet length however has everything to do with the twist you select and if you are going for 62gr and up, this normally means longer bullets and therefore, 1:8 is definitely better than 1:12.
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