Hornaday American Gunner vs. Frontier

[VASCAR2]

Hornady ammo gives me pierced primers regularly. Eld and bthp.
Same in 223 and 5.56.
Accuracy isn’t great either.
Hornady ammo just seems way, way too hot.

If your getting pierced primers on factory ammo it sounds like you might have an out of spec bolt or firing pin. You can also get tolerance stacking where the firing pin protrusion is to deep. You could have an out of spec chamber where the bullet in jammed into the lands of the barrel causing excess pressure. Odin works and a couple of other manufacturers used a 6.5 Grendel bolt with shorter overall length but a full length mil spec AR-15 firing pin.

When AA introduced the 6.5 Grendel they opted to use a .136 bolt face depth whereas 5.56/223 uses a .125 bolt face depth. AA lengthened the bolt by .01 (2.810”) to permit the use of standard length firing pins. A couple manufacturers use the standard AR-15 bolt length of 2.800” with a .136” bolt face depth. This combination needs a shorter firing pin to keep from having excessive firing pin protrusion. The minimum spec firing pin protrusion is .028” maximum is .036”. The maximum in spec length for an AR-15 firing pin is 3.279” with a tolerance up to -.009”. If you have a 2.800” length bolt your firing pin needs to be shorter 3.269” or less in length.

I suggest anyone who gets pierced primers with factory 6.5 Grendel factory ammunition in AR-15’s to measure your bolt and firing pin.

There have been a couple instances where forum members had a bolt that was a couple thousands longer than 2.810” and a shorter firing pin length and were getting unreliable ignition and failure to fire. This type of tolerance stacking has been pretty rare with 6.5 Grendel AR-15’s. It is not a wise to swap AR-15 bolts and firing pins without measuring the bolt and firing pin length. It is even more important with the 6.5 Grendel AR-15.