I recently bought an AR (5.56) with a 16" barrel that has a 1x9 twist. Ive been doing some online reading that says I wont have any luck with 75gr ammo that a 65gr is the heaviest. Does anyone know if this is true?

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Dyin ain't much of a livin

A 1:9 twist is commonly rated up to 70 a grain bullet

So whats the resulting effect? Thanks

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Dyin ain't much of a livin

Optimum twist rate of rifling is more correctly linked to bullet length rather than bullet weight. Of course heavier bullets have to be longer. Recommended twist rate charts are made up for bullets weights, but always assuming the ogive (nose shape) of the bullets are all exactly of the same design. That is not always the case. There are enough variations in ogive designs that exceptions occur to twist rate charts both on the light weight end and the heavy weight end. You have to experiment around a little. I think that you might just find a 75 grain bullet that will shoot just fine thru that 1 in 9 twist. .......... Big Cholla

I guess there is one way to find out....shoot'em and see.

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Dyin ain't much of a livin

I've tried 75 gr out of a 18.5 inch 1-10 and the bullets are going sideways at 50 yards. 1-9 is iffy and dependent upon velocity. I don't think you're going to stabilize the rounds with a 16 inch barrel. I can stabilze them in a 26" barrel.

I shot some Hornady 80 gr. A-Max out of a 16" barrel with a 1:9 twist and I got nice round holes out to 100 yards. Group size was not that impressive, being 3" or a little larger. The individual load was very important, with most others I tried giving terrible accuracy but even the least accurate loads (12" or more) produced round holes and there was no evidence of keyholing. My best load was certainly "man accurate" out to at least 100 yards, and that's all I wanted to know.

Dave Sinko