M&P15 feeding problems.

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At the TVI shoot on Saturday, my M&P15FT wasn't behaving well. Fairly consistently, it would jam on the 3rd round of a magazine. MassMark and others helped me with it and it looks to be ammo related but here are the clues:

- Problem happened with QMMO .223 reloads. I tried 20 rounds of XM193 5.56 and those went through just fine. I have previously used about 600-700 rounds of the QMMO stuff with no problems until Saturday.
- I cleaned the gun (really just the upper and bcg) the night before the shoot and lubed it well with Mobil 1.
- I tried a variety of different magazines, all did the same thing.
- If the bolt was closed, magazines don't seat with a satisfying click. If the bolt is open, all is well.
- The jam was a ftf. The round would be jammed on the feed ramp with the bolt on top of the case, always right before the case necked down, leaving a crease in the case.
- I could feel and hear the difference in the first two rounds of one of these incidents. The first round would feel and sound good. The 2nd round would feel a bit week and the 3rd would jam. It seems the bolt wasn't cycling all the way back between rounds 2 and 3.
- We tried Mark's BCG in my gun and it gave the same behavior.


Mark was thinking the buffer spring was too strong and he's probably right but I wanted to see what the brain trust here though. By the end of the day, I was thinking of selling it and getting a Sig 556.

Any help is appreciated.
 
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I'm not certain what the problem could be. I just wanted to add that my MP15FT has had similar issues before but hasn't had them in a long time.

Is it a brand new rifle? How are the mags? New followers in them?
 
My MP15 did the same thing. I noticed that it worked better with LESS lubrication. I finally got fed up with it and sold it and I bought a LMT.
 
I'm not certain what the problem could be. I just wanted to add that my MP15FT has had similar issues before but hasn't had them in a long time.

Is it a brand new rifle? How are the mags? New followers in them?

It's about a year old and has probably seen about 1000 rounds. The magazines were all USGI but at least one had been fully rebuilt with magpul follower, new spring, etc.
 
Paul just sent you a lengthly PM...The gun behaved well on 5.56. I suspect a combination of BCG/buffer and using .223....I also had more success shooting your ammo through my gun. No classic jams, but it did fail to strip a fresh round off the mag and the brass was falling well short of 5.56
 
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Have had mine since December, about 1000 rounds through it, mostly Fed XM193, some Remmy 223, some Win white box 556, not a single problem.

I also have the SIG 556, same everything as above.

My Colt pre-ban HBAR is a jammomatic. It's been sitting in the safe the past few years.
 
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