11.5 AR15 optimal bullet weight?

[the_omen545]

Im wondering what ammo you would recommend for an 11.5 ar15 with a 1/7 twist? ive tried 62 grain 556 by PMC but im looking for recs. how good would 55 grain be in a barrel that length? Thank you!

[GeneCC]

Im wondering what ammo you would recommend for an 11.5 ar15 with a 1/7 twist? ive tried 62 grain 556 by PMC but im looking for recs. how good would 55 grain be in a barrel that length? Thank you!

This is a toughie...

Bullet weight is not so much an issue as port pressure impulse through the gas tube and terminal effects. The person who set up your AR pistol may have taken that into account? I don't know.


In a full sized rifle 1/7 twist is too fast for a 55 grain round. It'll work but it will to some degree over stabilize the round. You can overdo stability.


Here is what I could do....

Get an idea of the possible muzzle velocity of the firearm.

Go here....

https://www.hornady.com/team-hornady...alculators/#!/


What this will do for you is give you a range of stability. You can work it out.


The fun way to do this is to just buy some rounds and try them out. Look for keyholing. Look for accuracy.

[Hib]

Distances?
How far away?
Do you want it to be set up for self defense, paper targets or tomato cans?
Want it to penetrate vehicles and urban obstructions?
Do you want it to zip through meat or go splat?

Any how, those were my thoughts (not being a smart alleck about it). The 5.56 is a strange little booger. It was created with the intent of making it shoot a minimally stabilized projectile that would tumble when it hit meat. Then it got "improved" time after time after time.

I've just about come to think that with the shorty barrels you may as well get it to tumble with a long bullet like it was originally designed to do with a short bullet.

[Roland45]

I get great 50-yard groups from a 10.5 psa upper that really likes the Hornaday 55 gr V max 0n top of 8208XBR.
We shoot at 1-inch dots on printer paper and as long as we do our part, they all stay inside the dot at 50. The upper has a 5.56 chamber and 1/ 7 twist, carbine length,
4 X scope off of sandbags. I have not gotten any good groups using factory ammo, at least to my satisfaction but that's why I reload.

[arjohnson]

My best groups out of any of my AR*s from 10.3 to 16 inch barrels are 77 grn SMK*s. They shoot great.

[oldengineer]

I do pretty well with Hornady 55gr FMJBT on 25.8gr of Varget. Carbine length barrel, 1:9 twist.