OK gentlemen. I'm requesting help with a weapon issue. Shooting at an Appleseed today and I wanted to try to qualify Rifleman with my AR 10B A4 20". Shooting MAL 5-82. Rifle & ammo have been 100% since purchase ~ 300rds (low rd count I know.) Had 2 light strikes during the first stage. Took the weapon off the line. Collected the dud rds and during the next string I was able to fire them through an M14 without any issues. The dimple of the ammo fired through the M14 is noticeably deeper than those fired through the AR10. Conclusion I have come to is light strikes. Hammer spring is in the right way (Spring curls on top of the hammer pin)and firing pin protrusion is .053 (I don't know what the spec is for this)checked with the bolt out of the carrier. Checked function of pin and travel w/ the bolt carrier assy together and no apparent binding or limits on its free travel. It shoulders up right on the rear of the bolt just like it does with the bolt out of the carrier. No serious crud in bolt or carrier either.
So here I am. What should I check next? How possible is it that the hammer spring is weak? Can y'all help?
Thank you Cowboy. Stock firing pin. Didn't try any other ammo. And I compared my spent brass from the past few months to some spent brass shot through an M14 at the range today and noted that my primer dimples look shallower. I guess the next thing is checking the head space and then replacing the hammer spring. The MAL I was shooting is Mil surp so hard primers are to be expected... and I need the rifle to be able to eat Mil Surp. If it won't, it will be sold.
Headspace could be the issue, but that's pretty rare. I've only seen it with ammo that's been chambered and re-chambered several times.
You've put 300 rounds through it. Were all the rounds from the same manufacturer?
Hammer spring: Are the legs of the hammer spring resting on top of the trigger pin? If not, that's probably the culprit. If the legs of the hammer spring are installed underneath the trigger pin (ie, resting on the floor of the lower receiver), then the hammer won't have the proper spring tension needed. The rifle will pass a functions check and fire most commercial ammo, albeit with shallow primer indentations, but FTF on military and mil-surp ammo due to the harder primers used.
Legs of the hammer spring are an top of the trigger pin. All but 9 rds have been the MAL. The other 9 rds are hunting ammo. I appreciate all y'alls help. Need to find some one around here that wouldn't mind letting me borrow his headspace gauges for about 5 minutes.
Also, inspect the tip of the firing pin. It may have become blunted or chipped.
Inspect the face of the hammer. I've seen some AR hammers that have a deep dimple on the face (Usually caused by an improper heat treatment that led to a softer surface.) This little bit of extra space didn't allow the firing pin to go forward far enough.
Hopefully, you've got a reliable AR 'smith near you that can help you get your rifle sorted out.
Replied by OleCowboy on topic Light primer strikes?
Dad was retired and had been for many years. Electronics was his thing, got his HAM radio license back in the early 30's. He was working at a hospital in Dallas and was a maintenance man working on as he said 'changing light bulbs'. It was a major Dallas hospital and did a lot of stuff. They were doing open heart on a Texas dignitary when the machine that keep the patient alive during surgery. In the middle of surgery the machine shut down. Folks are flying around flipping switches and dialing dials and the clock is ticking. They are at a loss it will not come on. Finally in desperation one of the guys says, call 'Charlie' the guy has been around maybe he has an idea.
Dad is called and he runs up to the OR asking where is the machine? They point, Dad runs around to the back, grabs the power cord and starts heading to the wall. He gets there, shoves the plug all the way in and the machine lights up...all is well.
What had happened was the cord which they were walking on was getting twisted each time and would shorten the cord a bit by torquing it. It rocked the plug out just enough to lose contact but stay in the socket.
My dad taught me the first thing you do if an electrical circut does not light is to insure its properly plugged in. Always start with the most basic and simple solution...
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