Hi all
I recently built my first AR system.  I do have experience with them from military training and knowing how to clean and maintain them.  However while at the range we put somewhere of 100-150 rounds through it and it started to have miss fires and then complete failure shortly after.  Upon inspection the firing pin was lock inside the bolt and we had to use clp and pliers to pull it out to find that it was so fouled it was locked up.  I have a WMD Nic-B coated full profile bcg and was firing federal green tips as well as some remington 223 rounds.  Of course after cleaning it up and oiling it up again it worked just fine, however I have not seen that kind of fouling and failure at that round count.  

Is this a problem with the ammo shooting dirty or is it with The NicB coated bcg, does it foul up faster than a normal milspec bcg?  Also it has a carbine gas system, but then again so have most others I have used exception of m16s.
How can I mitigate that fast of fouling in the future or do I need a new bcg all together

Thanks for the time in advance

Did you heavily oil it before your range trip? Try shooting dry and see if it fouls up that quick. Excessive gassing? Did it eject nicely (sling brass, eject forward). Need more details.

I would think the Nic-B would protect against this since the coating promotes ease of cleaning. It could depend on the sizing of your gas port in your barrel with a carbine length gas system. That still sounds excessive though for a small round count.

Not heavily oiled before trip. just regular maintenance after my last trip.  Brass ejected just fine no double feeds or ejected shells catching on shells being sent forward.  Just the miss fires where it doesnt look like the pin hit the brass.  It was noted while a buddy was doing video, I had noticeable muzzle flash and I have a  troy phantom on.  Not sure thats going to be helpful.  Not sure about the gas port into the gas block.  I got the upper complete minus bcg.

Maybe do a side by side , 50 rounds with yours and a buddy's mil Bcg. Is your tube boogered at the end? Could it not be seating well in the gas key?