Daniel Defense 10.3 inch barrel with 1:7 twist

[dsteed08]

Hey everyone,

Just picked up a Daniel Defense MK18 with a 10.3 inch barrel and 1:7 twist. Does anyone know where I can find a ballistics calculator to figure out how the bullets will perform out of a 10.3 inch barrel? Everything I look at has info for only 16 inch barrels.

Also, with the shorter barrel is 55gr too light to shoot? I know this sounds like a silly question, but I've seen a lot of marketing crap about shorter barrels not being able to stabilize lighter bullets. Should I go with 75 gr? I'm new to the short barrel AR game so please enlighten me. I would prefer to shoot 55gr since it's much cheaper.

Thanks!

[jwfuhrman]

its not how short the barrel is its how slow the twist rate is. your barrel will shoot 55's just fine. I had a factory built DD Mk18 and had no problem launching 55's to 400. It does like 75's and 77's better at that distance though, but thats every AR.