Took my new build out to a friend’s farm last night and tested several different types of ammo. Had several failure to fire events (like several per mag) of MFS .223 from PSA (like Silver Bear). But also a few Mk318 and two Federal tracers (just for fun, since it was dark).
I googled around a bit and found a good checklist, as well as searching this site.
I’m going to start investigating the cause, but I wanted to see if this seems like a complete checklist?
Member Eric posted this picture, and confirmed that the arms of the hammer spring should ride over the top of the trigger spring in this picture.
From Bushmaster’s website FAILURE TO FIRE: The most probable reason for this is bad ammunition. Wait 30 seconds with the weapon pointed in a safe direction, remove the magazine, then pull the charging handle to eject the round, and examine the primer. If it has a good, deep primer strike, the ammunition is probably no good. If it has a light primer hit, it may be a hard primer, or the hammer spring may be defective or installed incorrectly, or there may be debris between the hammer and the forward wall of the lower receiver. A quick look in the lower will tell you. If it doesn’t have any mark at all, the firing pin isn’t reaching the round. The firing pin retaining pin may have been installed incorrectly (in front of the collar instead of behind it), the firing pin may be defective (short), or the hammer is not hitting the firing pin for some reason (not falling, hitting bolt carrier instead, debris in front, etc.). If, when trying to eject the unfired round, the charging handle is difficult to operate, the bolt may not have been locked fully forward due to an oversized round, or debris in the chamber. Riding the charging handle forward may also cause this problem. Remember, pull it back, and let go. NOTE: All AR-15 type rifles dimple the primer during feeding. This is completely normal for this type of weapon.
Try the effected ammunition lot in another known good rifle to see if the problem follows the ammunition or stays with the rifle.
Try the upper on a different lower to see if the problem follows the upper.
Check the protrusion space of the firing pin… Makintrax73 posted that he recalled the protusion should be .030" to .039". AR15Barrels posted on Calguns that the spec is “minimum (.028”) and maximum (.036") protrusion".
It was a BCM LW middy upper reassembled after being disassembled and cerakoted.
BCG was stock PSA.
Lower is Noveske Gen2 FFL with A5 RE with stock A5 buffer & spring.
Trigger is an ALG ACT with red JP hammer spring.
Accuwedge is installed.
But for the purpose of a failure to fire, would anything other than the hammer & spring, BCG, upper matter?
Problem was pulled trigger and it went click. Rack the CH and it goes bang again for a few times.
I got mostly through some mags, not more than a few rounds in others.
Mags were Lancer AWM, GI alluminum, and a Troy mag.
BCG was lightly lubed with gunzilla, the bolt inside was removed and coated semi-heavily with gunzilla, then reassembed and reinstalled.
Pretty sure the cotter pin was put in behind the firing pin shoulder should and not in front of it as mentioned in the checklist above.
Any advice is greatly appreciated. I’m going to take it down and inspect everything, probably tomorrow as I plan to hit the sack early so I can beat the crowds at the polling station in the AM (630am)
What do the primers on the unfired and fired cases look like?
Some Russian ammo is small, making to much headspace. The firing pin does not strike as deep. Check the bolt to make sure no trash is in the FP hole. The bolt OAL should be 2.8" if the protrusion is short and the bolt is the correct length the FP could be short.
JP hammer springs are made for lighten hammers, not for mil spec hammers. The combination of a mil spec hammer and JP competition hammer spring will cause light strikes.
