1:7 or 1:9 twist

[trlcavscout]

All I have been shooting is 50 gr HP walmart stuff out of the Bushy (1/9) I had, the Colt and my now BCM both 1/7, I cant tell a difference? They all shoot about the same 100yd groups, probably the best that ammo will do.

[Bad Dog]

My AR has a 20" barrel with a 1/7 twist rate, if I am understanding all of the information posted mine was designed to shoot a heavier bullet.
My question is if I shoot a lighter bullet (55 Gr.) will that lead to poor accuracy or will it have no affect at all on accuracy?

[Colorado Osprey]

My AR has a 20" barrel with a 1/7 twist rate, if I am understanding all of the information posted mine was designed to shoot a heavier bullet.
My question is if I shoot a lighter bullet (55 Gr.) will that lead to poor accuracy or will it have no affect at all on accuracy?

Generally speaking there is no such thing as over stabilization so you can shoot light bullets just fine it will not effect accuracy.

Like I stated before.. the only possible problem shooting light jacketed varmint bullets; there is a possibility with a 1-7 that you could have a bullet come apart upon exiting the barrel. There have been no definitive studies to determine if the type of barrel rifling vs twist is more of the culprit to this phenomenon in the fast twist barrels.

Shoot away... light, heavy You'll be fine
BTW a 55grain bullet is not light, it is the most common bullet size in .224
Light bullets in .224 are 36-40 grains

[Bad Dog]

Thanks for breaking it down and making it easy to understand

[2ndChildhood]

My accuracy in that barrel was poor with Hornady 55 gr fmjbt's and with wolf 55 and 62 gr ammo.
When I went to the hornady 75 gr fmjbt's it shot like a champ.

Here's another guy with a different 1:7 gun that had the same experience:

AR15 had a chrome-lined 1 in 7″ twist barrel. It was freakin’ picky on ammo and preferred match stuff in the 68-75 grain range (Ultramax, Prvi, etc). With those heavier bullets I could turn out some 1-2 moa groups. After break-in I was quite pleased this rifle with the M4 profile 16″ barrel turned out a 3″ group with Ultramax 68 gr at 300 yards. However, with various types of 55 gr ammo (Federal, PMC, Wolf) my groups ran anywhere from 5″ to 7″. This is like a car that prefers premium gasoline to “run right”. I’ve shot many other AR15s with 1 in 9″ twist barrels which have grouped everything in the 55-75 gr range far better.

http://gardenserf.wordpress.com/2011...-vs-5-56-west/

[GandNuateta]

Buh Bye

[Akyla]

One of my planned builds is a heavy 24-26" varmint barrel AR. Lots of varmint loads are the lighter faster bullets, so do I use a 1:9 or go even a bit slower? What's best for a varmint barrel like I mentioned? Thanks!