Best twist rate in AR barrel for basic factory ammo with 55 grain bullet?

[jack76590]

I have a number of AR with 1-7 twist barrels that are not giving very good accuracy with Federal xm193 ammo with 55 grain bullets. Seems the lower price ammo all have either 55 or 62 grain bullets, generally 55 grains.

So, if you use this type of ammo have you had better accuracy with slower twist barrel rate like 1-8 or 1-9?

[ExFlyinguy]

I have a number of AR with 1-7 twist barrels that are not giving very good accuracy with Federal xm193 ammo with 55 grain bullets. Seems the lower price ammo all have either 55 or 62 grain bullets, generally 55 grains.

So, if you use this type of ammo have you had better accuracy with slower twist barrel rate like 1-8 or 1-9?

I'm sure there are some folks that have great results with 55gn in 1-7 twist rates, but generally speaking 1-7 is better suited for the heavier bullets.

Lots & lots of diagrams are on the webs here's one that I found at top of my search.

https://www.nrablog.com/articles/201...r-ar15-barrel/

[borekfk]

1/9 or if you want to go really old school than a 20" 1/12 barrel.

[cdi]

XM193 isn't exactly match ammo.
What level of accuracy are you after?

[jack76590]

XM193 isn't exactly match ammo.
What level of accuracy are you after?

With 1-7 twist in PSA barrel getting 5-6" groups with xm193. As I recall just a little over 3" with Ruger 1-8 twist. With Colt heavy HBAR and high powered scope with 1-9 twist was getting close to 1.5" groups. All with xm193 at 100 yds. PSA and Ruger had I think about 4x scope. I picked up blem Del-ton upper in carbine configuration with 1-9 twist I plan to test when weather better and hoping for decent results, as in 2.5 MOA or close with xm193. Really would like consistent 2 MOA with cheaper ammo with basic carbine and 4x scope, but that may be unrealistic with xm193 ammo. But I am thinking commentors recommending 1-9 twist are right among the twists readily available.

[JenniferG]

Try different ammo with that 1:7. I had a Colt Sporter HBAR 1:7 20" barrel that shot like an curved barrel Chinese SKS with 55gr bullets meaning barn sized targets where difficult but with 62+ it was shooting -1" groups at 100yds. The best were 68 or 69 gr out of that gun. Now with my HB Colt 16" 1:9 55 gr Winchester M193 works nicely with 1" + or - at 100yds and 62gr various brands it opens up just a bit. You have to experiment with different ammo to see what your gun will shoot accurately but generally the 1:7 likes the heavier bullets. After all the 1:7 was specifically designed for the M855/SS109 62gr grain projectile.

[bigandy1966]

I have even found some specific manufacturers perform better in some barrels than others.
Some twist/ bullet weights/ manufacturers combinations would buck the conventional wisdom depicted in the graph.
I have a .270 Remington 700 Adl that will shoot nickle sized groups with cheap ass Remington coreLokt 130 grains off the bench, all day long, but winchester or federal of the same bullet weight/ loads would go +/- 4-6" @100yds, some would even be premium hunting ammo
Find what the rifle likes the best.
Some guys who handload tweak the loads up or down to get the best performance.
One Guy at the range fire forms the brass in one specific rifles chamber and keeps that brass with that rifle and loads it to an exact recipe

[cdi]

I use the federal xm193 as test ammo for function check in the shop. It*s been very consistent. Accuracy wise, it*s probably in the 2 minute range.

Best to shop around and see what flavor works best in your rifles.

[Palerider]

With 1-7 twist in PSA barrel getting 5-6" groups with xm193. As I recall just a little over 3" with Ruger 1-8 twist. With Colt heavy HBAR and high powered scope with 1-9 twist was getting close to 1.5" groups. All with xm193 at 100 yds. PSA and Ruger had I think about 4x scope. I picked up blem Del-ton upper in carbine configuration with 1-9 twist I plan to test when weather better and hoping for decent results, as in 2.5 MOA or close with xm193. Really would like consistent 2 MOA with cheaper ammo with basic carbine and 4x scope, but that may be unrealistic with xm193 ammo. But I am thinking commentors recommending 1-9 twist are right among the twists readily available.

Are you using a shooting rest/vice? If not the difference in your scopes could be contributing to group size as well. I find there*s a big difference between 4 and 9 X when you*re trying for precision and using bags only. Can you put higher powered scope on one of the other uppers and try again?

[ShadeRabbit]

With 1-7 twist in PSA barrel getting 5-6" groups with xm193. .

Pretty much exactly what I'm getting with 1:7 PSA upper. Dog-crap accuracy. A guy at the range told me it's because PSA does not lap in their barrels, so that might be part of it in addition to the bullet grain.