M&P 15 R will not go into battery

[nozzle13]

Ok, I'm at a loss, I hope this is in the right section, I tried searching but to no evail..... yada yada yada I need some help troubleshooting.

Here's my problem.

The bolt on my M&P15r will not lock onto the case rim of the 5.45. This just started yesterday. The day before, I shot a good 250 rnds no hiccups no problems. When I took it home I sprayed it down with degreaser, wiped it down, blew it out with Air compressor, and repeated these steps with WD40, and Then CLP. Function checked and put back in bag. Did not run a chamber brush or rod through it.

I go to the range the next day, get all set up, load up a mag, and hit the bad lever. Bolt dose not go all of the way forward. Hit Bolt assist, and nothing stays the same. Drop the mag, lock back bolt, and see the 5.45 round, in the chamber. End up having to remove it with a dental pick. No damage to the rounds. Take the bolt carrier out look at the bolt. Take everything apart, and all looked good. Repeated about 4 times. Bolt will lock up manually with out a round in the rifle. It would not lock up even if you hammer the bolt assist.

Does anyone have a reason/solution for this?

[Robb Jensen]

Are you certain nothing is in the gas key on the bolt carrier?

[Zhurdan]

Or a broken off case neck. (Does the bullet go all the way in the chamber?) Check to see if there's something down the barrel too.

[nozzle13]

Welt, just looked at it again, and gas tube is clean as a whistle, as well as the chamber. No sign of broken cases anywhere. I believe the bullet was going all of the way into the chamber. When the bolt didn't close on the rounds, I was only able to get a dental pick around the case rim in order to get them out. It's like the bolt face is not opening up to surround the case rim. I even tried pounding on the bolt release to no evail. Without a round in though the bolt engages properly.

[Robb Jensen]

Don't know I'd need to see the entire upper.

[Grumpy MSG]

One possibility I haven't heard mentioned yet is a problem with your ejector, it could have gotten gummed up when you sprayed the rifle parts down with cleaners and lubricants. To check it, remove the bolt carrier from the rifle,hold it in your hand, take a round or preferably a fired case (putting a long bolt or cleaning rod in the case may help with leverage), hook it on extractor and rock it back into the bolt face. It should take a little bit of effort but it should depress the ejector, if it is gummed up or froze up it won't move at all. that would prevent the bolt from closing fully on a round and prevent the extractor from actually hooking on the rim of the case. Without the cartridge in there the bolt would close fully.

[nozzle13]

Well I was able to depress the ejector with my range flag while I was at the range, so I think it's good.

My buddy came by a little while ago, and he says it doesn't look like the round is completely chambering. The chamber looks clear of debris. Is there any chance it could be a head-space issue? Or maybe laquer build up? I'm at work today, so my options for inspection/fixing are limited today.