Barrel twist question

[Brad in Idaho]

My Colt AR has a 20" barrel with 1 in 9 twist. I have lots of
55gr FMJ bullets to use in handloads. Is this length barrel with this twist rate compatible with 55gr FMJ's accuracy wise? I do have some 62gr IMI FMJ's too.

[lyman]

you will do fine with either,
you'll do fine with 69gr as well,

some barrels with a 1/9 will shot a 75gr, but you will need to do a test to see,

[Kirk]

A 1 in 9" twist will stabilize a 55 gr bullet fine. However, the typical 55 & 62 gr FMJ military bullets may not give good accuarcy simply because of poor tolerances. They are just too inconsistent to shoot well in any barrel. Switching to 55 gr softpoints or match hollow points like the 69 gr Sierra will shrink groups.

[joem]

I have a 1/9 twist and the 62 gr are more accurate than the 55's.