Twist Rate in a 5.56 20" Barrel

[wcsc12]

Someone told me that a 1/7 twist in a 20" barrel was bad and that a 1/9 twist was better.

Can anyone give me some more info on which is better?

I will really only be shooting for fun. I won't be doing anything super marksmanship like. I may go hunting with it once or twice just to see what it does to a deer but that's seriously about it. I don't really have any specific ammo that I'll be using. More than likely just Federal or other cheap .223 and some Federal green tipped 5.56 rounds. Maybe some Z (V) Max rounds also. I don't reload right now and I may about 5 years or so in the future but I don't have any aspirations to do it currently.

[mikegideon]

The military went with 1 in 7 to stablize tracer rounds. Unless you are going to be shooting long range bullets (ones that won't fit in the magazine), you don't need 1 in 7. The down side is that lighter varmint bullets can fly apart because of too much spin. A 20" barrel can make a good varmint rifle if the barrel is free floated.

dolomite in 3...2...1...

[Caster]

I've learned the hard way. 1/7 really sucks. I have some 50g soft points that will not hit ANYTHING at 100 yards. Literally, because the bullet will come apart.

I have a 1/8 on another AR and it shoots everything. I have a 1/9 on a CZ bolt action and it will shoot anything.

Edited July 28, 2012 by Caster

[wcsc12]

The military went with 1 in 7 to stablize tracer rounds. Unless you are going to be shooting long range bullets (ones that won't fit in the magazine), you don't need 1 in 7. The down side is that lighter varmint bullets can fly apart because of too much spin. A 20" barrel can make a good varmint rifle if the barrel is free floated.

dolomite in 3...2...1...

Barrel will be free floating.

What do you mean varmint bullets? Like lighter grain bullets for hunting squirrels and such?

Will a 1/9 shoot the heavier bullets like 77gr?

Edited July 28, 2012 by wcsc12

[mikegideon]

Barrel will be free floating.

What do you mean varmint bullets? Like lighter grain bullets for hunting squirrels and such?

Will a 1/9 shoot the heavier bullets like 77gr?

Varmint bullets with thin jackets under 55 gr. No, according to Sierra, a 1 in 9 won't stabilize a 77 grain Matchking. But, you can shoot 69 grain SMK's. It's more about bullet length than weight. The 77 is the heaviest Matchking that can be loaded to magazine length, so you're only missing out on that one bullet. I shoot 77's in my 1:8, and it's real accurate.