Smith and Wesson MP15 .223 light strikes...

[trammd]

Hello, this is my first post. Lots of great info here!
I recently purchased a M&P15 MOE, great gun. Upon firing it for the first time (after cleaning and oiling the gun)

I was noticing after the first 2-30 round mags I would get a failure to fire. Gun cycled fine, just NO Bang. upon cycling the charging handle the spent cartridge was inspected (55 grain PMC FMJ) and had what appeared to be a light primer strike.(see pic) At first these failure to fires ocurred about every 3-4 rounds after the first to magazines were fine. Then the gun would not fire ANY rounds chambered by the gas operating action of the gun.

I could MANUALLY chamber a round by pulling the charging handle and releasing and the gun would fire ONCE, But the follow up shot will fail to fire every time now with the lightly struck primers. I did make sure the gun was cleaned and lubed, pulled the BCG and sprayed down with Ballistol then reinstalled but same result. The manually chambered round fired fine but any following shots chambered by the rifle gas/buffer system resulted in a click, No Bang. Light Strikes.

Any Ideas as to what is happening? The gun is stock. I came home today and disassembeled the gun and BCG looking for issues but everything seems OK. Firing pin and trigger group work smoothly with No apparent issues. Once again this was ALL PMC 55 grain on a NEW never previously fired gun and the first 2 30 round mags fired with zero issues. It was the second 2 when the trouble started and finally turned my AR into a manual bolt action rifle! Any and all help and input is appreciated!

[SharonAnne]

ok, I am guessing. The ammo may not be making enough gas pressure to get a full stroke on the bolt/carrier. It may be just barely picking up the next round and the bolt/carrier does not have enough inertia to get the bolt to close completely. After the first round, try using the foreward assist FIRMLY. If the round then fires you may have found the problem. Have someone at the range try your factory PMC in another AR15. IF it works you may have the next problem.

It could also be that the gas block and gas hole are not properly aligned.

If the ammo works in another AR15 consult a gunsmith who is competent in ARs.

[jmayton]

It almost looks as though the light strikes you are getting are the normal strikes that come from the bolt going into battery (floating firing pin causes this, but there not enough velocity to cause a detonation), but since it is happening only when the gun is cycled automatically, I gotta say gas system or buffer are not causing the bolt to go fully into battery.  Check this by manually cycling the first round and inspecting the BCG location, fire that round and then re-check the BCG location, push the forward assist and see if the BCG moves.  If it does, try different ammo and see what happens.  If it still does it, then check the gas system and the buffer (for a Carbine it needs and H buffer).  Best of luck.

[trammd]

I shot about 200 rounds today without an issue !
I paid very close attention to my "trigger form" and carefully listened for the reset after each shot.
Also I did notice The PMC cases were not thrown as far as the Hornady Z-max, Rem UMC,or HPR. The PMC was actually ejected up to 2-5 feet less than the other brands!
 
Oh, and I did cycle and fire the PMC (20+ Rounds) from yesterdays malfunctions.
 
I did force a failure to reset once by being really sloppy on the trigger. (rapid fire and not paying attention an allowing full travel of the FCG)
 
I am new to the AR platform an I am learning how important good trigger control is!
 
So it was probably several factors causing my issue and I believe they were:
 
1- New Gun (needed some break in)
 
2-PMC ammo may have not been the best choice for initially breaking in the gun as I think it is on the low pressure end for my mid length AR.
 
3- MY using lazy trigger form! I now am a believer that you need to learn to allow for a proper reset with each shot!
 
Thanks so much for ALL of the great advice!
I hope I can return the favor to someone else (new AR owner) that may need help in the future getting through their rifles growing pains.
 
Thanks Again!

[jmayton]

Glad it's running good. Keep shooting it and it should just get better and better.