Wednesday, September 16, 2015


Working out the bugs in my x39 AR... I am currently in process of adjusting it to eat all types of berdan primed ammo and not just a few select flavors. I think I found the problem...

Side by side comparison with a BCG that was used in another rifle I built for a friend. He bought his bolt from another supplier and used the same carrier that once held his .223 bolt. Pretty easy conversion with just a barrel and bolt swap there. 

The firing pin hole in the bolt face is slightly larger on his to the left. That could cause the pin in mine to not protrude far enough out through the bolt face hole into those hard primers and not ignite them. So there's my 1st suspect.

He also bought a true enhanced titanium firing pin. "Enhanced", meaning the stop cut into the firing pin is a bit thinner than a standard .223 firing pin to allow more protrusion past the bolt face into the primer.

The supplier of my designated 7.62x39 BCG stated that my firing pin was "enhanced" as well. I'd have to disagree now that I've got a true enhanced pin to compare with side by side.

 Per the manufacturer of mine:
Firing Pin

  • Machined from 8640 tool steel
  • Enhanced Firing pin for ComBloc ammo
  • Heat treated to military specifications
  • Ground to meet military required tolerances
  • Coated with .0002”-.0003” of hard chrome per MIL-STD-171

See the difference?

There is an obviously noticeable difference in the shoulder length on the end of the pin that strikes the primer as well. Suspect #2 identified. 

Solution : Slightly enlarge the firing pin hole and dremel down the stop on my firing pin a little to allow more pin through the bolt face. I'm betting that will fix the problem with the non-fires since I'm using a Wolff XP spring that hammers very hard already, so something told me it was probably in the BCG. I'm also going to contact my BCG supplier and relay to them my findings. I guarantee there's been plenty of other builders out there that have just about had it with the x39 AR platform from using this BCG. Not naming any names either, just know parts are from a reputable supplier. 

Y'all have a good day.

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