Ar15 barrel twist rates vrs bullet weight ?

[Harleynut]

I have a RRA Varmint A4 with a 20 inch bull barrel that has a 1 in 8 twist. I have heard that most people shooting long range end up with heavier bullet weights. So far I have only shot 55 gr bullets. I have seen some Privi 75 grain target loads at a local gun shop. I am wondering if the 75 with this twist rate is a good match.
Any info will be appreciated.

 

[Blitz1]

PM me on the store, I'll check it out for you.

 

[Gammon]

1/9 is supposed to shoot both light (55gr) and the heavier bullets well. 1/8 will probably respond better to heavier bullets; 62 gr and up.

 

[bpm990d]

You should be good to go for any conventionally constructed bullet (lead & gilding metal jacket) up to 80 gr. However VLD bullets in that weight range are pushing the envelope (because they tend to be substantially longer than regular bullets like the Sierra 80).

75 Privi should be fine.

You can use the Miller Stability calculator in conjunction with the bullet length list on the JBM Ballistics page. He dosent have Privi bullets listed, but they are basically Hdy. 75 HPBTs.

B

 

[LKB3rd]

The faster twist rates will handle 55 grainers as well. For the lightest bullets (less than 55) the faster twist rates have been said to over spin them. 1/8 should be fine for a pretty wide range of bullets, but the best way to find out is to buy a box, and send em downrange to see how they work in your particular rifle.

 

[PatMcD]

I think the 1/8 is the most versatile twist rate for the .223. It will handle 55's on up to Sierra 80's. The one I had was an absolute hammer with 80 grainers.. have no idea why manufacturers insist on always using the 1/9.

 

[Remsport Mfg]

I shoot a gun with an 11.5" barrel with 1:9 twist using 55gr. bullets and have no problem hitting a man size target at 300YDS.
1:9 will handle most bullets and it will make no difference at 100YDS. The difference come when you want to stabilize a bullet at long range 300YDS. plus a 55gr will start to tumble so a heaver bullet is needed this is why you would need a 1:8 to stabilize a 76gr. bullet at long distances. For most target shooting 55gr. and 1:9 twist will be all you would need and it is the standard. Most of the shooters don't shoot past 200 YDS. And never spend the money for 76gr. match bullets they are always looking for the least expensive ammo and this is in 55gr. I also don't know many guys shooting heavy bullets with a 16" barrel. A good stainless steel 1:9 barrel will serve almost all of your shooting needs.

 

[bpm990d]

Pat

I remember the days of 12 twist .223 rifles. Just give them another 20 years and they will start to put 8s on.

B

 

[PatMcD]

Pat

I remember the days of 12 twist .223 rifles. Just give them another 20 years and they will start to put 8s on.

B

I had an old SP1 with a 1-12 barrel. I never shot it much for accuracy. Sold off the upper but still have that "slick-side" lower.

To my way of thinking, they would offer two different twists. 1-12 and 1-8. 1-12 if all you were ever going to do was shoot 40-55 grainers (varmint, plinking). 1-8 if you wanted the option of good heavy bullets.

I don't think I've ever heard of a 76 gr bullet.

 

[Admin]

Pat I agree 1/9 boggles my mind and as Brian said they used to use 1/12....

 

[Old Glory]

I have a 1-12 that is a varminter shoots a flatter trajectory with the lighter bullets. I use it for punching paper.

 

[Remsport Mfg]

1:12 is great for 22LR.

 

[TXDMERC]

i have a Bushmaster with 11.5"Hbar and 5.5" hider i shoot 55 gr fmj at 25 feet they fragment and are accurate but after i go to 50 yards it starts to spread out to 3 or 4 MOA and no fragmenting the soda cans. i am gonan move up to 69 gr or 75 gr but they are expensive to practice with.

 

[Supermoto]

if your groups are opening after 50 yards. the bullet weight is not going to make a different. Its either you or the barrel.

 

[Jose]

I have a 1-12 that is a varminter shoots a flatter trajectory with the lighter bullets. I use it for punching paper.

The rifling twist has absolutely nothing to do with the bullet's trajectory.