I am getting (maybe) a CMMG 18" Gvt Profile “Bargain bin”-- it has a 1/7" twist-- will 55grn bullets still work ok with it, or am I better off getting the 16" M4? I really like the looks of the 18", but the twist rate worries me, as this one wil lbe a knock around range rifle/paper puncher…
Help!
They will be fine.
55s will be just fine.
So will 62s, 68s, 75s, and 77s.
Is there any advantage to the 1/7" then? I don’t plan on shooting any light varmit 40 grns, and will probably shoot mainly 55grns, but my dad has a couple of cases of some sort of 62 grn stuff that I think he bought for Y2K— I am trying to pry some away-- but 55grn will probably be its normal diet…
The 1/7 should do better with the longer (generally heavier) bullets and many folks feel that the heavier bullets are better for personal protection.
Some 1/9 do ok with the longer (generally heavier) bullets - have to try to know for sure.
So if you know you won’t be shooting stuff heavier than the 62 gr ammo then the 1/9 should be fine (the 1/9 could possibly do well with 69 gr - and might do ok with the 75 gr stuff)
Most folks prefer the 1/7 to give the greater opportunity for better use of heavier ammo (1/7 usually does well from 55 gr and up - and sometimes does fine with lighter bullets)
These are just my opinions - ymmv