08-15-2018, 01:31 AM
VASCAR2 Wrote:I hate to bring this up again as it has come up before but when Alexander Arms intoduced the 6.5 Grendel bolt AA used a .136 bolt face depth. AA added .01 length to a standard AR-15 bolt which is 2.800 length so a AA 6.5 Grendel bolt should measure 2.810 from the outer most face to the rear of the bolt. AA used the 2.810 bolt length so a standard AR-15 firing pin can be used with an AA 6.5 Grendel .136 bolt.
There have been reports of pierced primers from excessive firing pin protrusion with 6.5 Grendel .136 bolts that are 2.800 length like Toolcraft. A milspec firing pin is 3.280 and will work as designed with a 2.810 AA 6.5 Grendel bolt. Using a milspec length firing pin in a 2.800 length Toolcraft .136 6.5 Grendel bolt may produce pierced primers. You can get an extra .01 firing pin protrusion from the shorter 2.80 bolt. Throw in the variation in manufacturing tolerance and you might experience pierced primers. Some manufacturers were supplying non milspec (shorter) firing pins with the 2.800 6.5 Grendel bolts.
Just something to be aware of if your .136 bolt face depth 6.5 Grendel bolt measures 2.800 overall length, probably should have shorter firing pin. A person can shorten a milspec firing pin by .01 to account for a shorter bolt length.
Brownell’s sell a firing protrusion gauge. Minimum firing pin protrusion on an AR-15 is .028 maximum length .036.
https://www.brownells.com/gunsmith-tools...26477.aspx
Thanks for posting all that again sir.
So looking at the specs stated that puts my gear dead in the sweet spot of proper length, good enough for me.