05-14-2019, 11:06 AM
VASCAR2 Wrote:Bolt depth should be .136 + or - 001 so it is a little deeper. The firing pin is full length but has the shorter 2.80” bolt length. With a 2.800 bolt length the firing pin needs to be .01 shorter than standard length firing pin 3.279-3.280 length.
I think this combination will give excessive firing pin protrusion. Minimum firing pin protrusion is .028” to maximum .036” or .008” tolerance.
You can buy a firing pin protrusion gauge from Brownell’s to verify the protrusion is out of spec. If the firing pin is to long you’ll get pierced primers or have a greater chance of a slam fire when chambering a round. I think the firing pin needs to be shortened to 3.269”-3.270” or shortened by .01”.
When Alexander Arms introduced the 6.5 Grendel they lengthened the tail of the bolt to account for the deep bolt face depth. Original 5.56 bolt has a .125” bolt face and a 2.80” length bolt. AA 6.5 Grendel bolts are 2.810” long with .136 bolt face depth. Adding .01” length permits standard AR-15 firing pins to be used with AA bolts. Some manufacturers did not add .01” to the bolt length.
Bolt face depth could be operator error. Using my caliper I was getting widely different depths. Ill confirm the bolt length and firing pin length and confirm if the firing pin needs to be shortened. Thanks.