In my experience 1 in 9 twist was not enough for the 105gr A-max
1 in 9 will work great with Sierra 100gr Game Kings
My old gun measured at 1 in 9 and the groups suffered when I switched from Game Kings to the 105 A-max. (GKs were MOA or better, 105A-max were 4 MOA)
My solution was to build a new gun, to shoot 105-107s
Just as a point of reference it says 8 twist on the box
Basic calculations will show you where you need to be on twist rate with regard to bullet diameter bullet length and velocity. When I run the numbers, it looks like an 8.5 twist is the minimum rate to stabilize the A-max and the Sierra Match King needs even a bit more. So an 8 twist is most likely where you need to be.
OAL for a 243 is not cut and dried “2.710” unless you are reading it from a reloading book. It has more to do with your chamber and you action… I load 0.005 off the lands and my OAL is 2.760” with no feeding issues. The rest of the recipe Lapua brass, fire formed neck sized only, 40grs IMR 4350 (middle of the road by my book) not the same a H4350
And as far as anyone saying “the A-max is not as accurate as it should be”??? Tell that to all the 6mm BR guys.
IMHO The A-max, in the right gun with the correct twist, is about as good as you can get.
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