Took my son in law out shooting this weekend which marked the 2nd time I have shot my M&P-10. First time I went which was about six months ago I got all the way out to the range and realized I did not bring any magazines with me so all my shooting then was having to hand feed rounds in. I found then that of the several different brands I had, Federal Gold Medal Sierra Matchking 168 grain seemed to produce the better groups for my rifle.

I picked up 3 boxes of Gold Medal from BP last week and took them out with us on a shoot yesterday. Loading 10 rounds per mag the first box fired ok. On the 2nd box on about the 3rd round I got a jam. Cleared the weapon, reinserted the Mag first round fired ok and then 2nd was a jam. I observed my casings were kicking out at the 4 oclock so I thought maybe I was having a magazine issue so I tried a different mag. Same issue, 2 or 3 rounds and a jam. On one occasion the rifle failed to fire because the bolt had not picked up the round out of the mag. Well ****. Opened the 3rd box of gold medal and using my 3rd Magpul mag and 2-3 rounds and a jam. Carefully checked the rifle and mags over and nothing to note other than some brass hairs in the chamber area but I assume that to be normal. Switched over to some Hornaday, no jams. Winchester, no jams. Couple more different grain and manufacturer that I had, no jams. Even shot a box of Federal Power-Shoks, no jams. As long as I stayed away from the Gold medal I was jam free.

The only conclusion I can come to is that at least 2 of the 3 boxes of Gold Medal I picked up have casings that were not properly made as it appears the bolt was having a hard time picking up the rounds from the mags. No more Gold medal for me.

That's odd. I can't remember if there is any lot numbers on their boxes or not. Just to see if they were from the same lot and therefore a problem with a particular lot.

A call to Federal might be in order. I've not had a problem with their ammunition, even the Gold Medal Match.

Was your rifle reliably locking back on an empty mag with the gold medal? And what kind of jams are they? I ask cause you said it failed to pick up a cartridge and if its short stroking that could be why it's jamming.

Most of the jams were with the round nose down in the chamber. I thought there was a chance that the bolt might be short stroking off the ammo but fired rounds were ejecting to the 4 oclock.

Did not get a single FF on the other brands of ammo I was shooting.

The bolt locked back on all the empty mags.

Did you ever figure out what the problem was I am having same issue. Tore my hole gun down and cleaned everything even found my gas tube role pin was backing out and gas tube had spun a little. Repaired it and test fired and my gun wont even lock back after shooting a single round at a time

Probably should be thankful everything else is "happy" with your rifle, you could be in much worse shape, just read the threads, sounds like your rifle is pretty happy...

May be time for a trip back to the factory, I wouldn't volunteer too much information on your volunteer gunsmithing, the factory takes a dim view of DIY, LOL.

I am also having problems with Federal GMM 175 grain in my MP10. Weak ejection; however it is at 4:00. But its weak. And bolt is short stroking because sometimes it won't even pickup another round and I just get a click. I think my gun is under gassed or the ammo is low pressure, but for F's sake it is GMM and it needs to run that ammo.

Not sure if this will help but I had an issue where the last rd wasn't locking back on My M&P 10 in 6.5 creedmoor and I solved it by re-aligning the gas block, and using a spikes T-2 buffer.

I could see the gas block was off by a bit by looking at the carbon deposit around the hole.

I used an old A2 hand guard cap cut in half to space the gas block more forward.

I measured how far off the misalignment was with a caliper and it was almost exactly the thickness of an A2 hand guard cap.

This combination solved the problem and it has been running flawless since fall of 18.