Smith and Wesson M&P15x Troubleshooting(Pic Intensive)

[Greatestsin]

There sounded upon my door a soft rapping just before 6:30am.

Not a bad way to start the day, right? Too bad its not for keeps.

As some of you may well already know, we are having problems with this gun. For those that don't, see this thread:https://www.indianagunowners.com/fo...sion/66128-problematic_s_and_w_m_and_p15.html

Today has been given over to the troubleshooting of this gun(barring bad weather). First things first, the basics: Check the gas key and the gas ring.

I gave it several tugs and tried severely to cause it to jiggle, to no avail.

Upon a physical examination, I found there to be no burs or dents or scrapes. It is as smooth as a baby's bottom.
Next is to check the gas rings.

It stood on its own with no movement. 2 down, several more to go.
Today we will be taking it to the range to fire off several hundred rounds, both PMC 55grn and WWB 55grn. The weather calls for ice, sleet, and icey rain. Should be a good day. Updates later.

 

[Greatestsin]

Unfortunately he didn't make it off work in time. He won't be here for half an hour and the range closes in 45 minutes. I guess i'll just update whenever we get around to doing it then

 

[kycrawler]

measure the uncompressed length of the buffer spring . i had similar problems with a colt 9 mm and it had a rifle buffer spring in a carbine . That one could have been a mixup at the factory

 

[Litlratt]

Based on the other thread, it sounds as if it is short stroking.

 

[zstep7]

It's too bad they can't just come ready to go, maintenance free and with a lifetime warranty. I love that rifle, would like to get one, just can bring myself to doing it yet.

 

[Fixer]

Based on the other thread, it sounds as if it is short stroking.

I have to agree. I had a similar problem with my rifle, when I first got it. It would fail to strip the next round and failed to hold open on the last round. After rechecking the gas block for alignment. I believe it was a combination of the bolt dragging in the carrier and some powder I was trying to get rid of. I don't think the rounds I loaded had enough energy to reliably cycle the rifle. It was left over powder that I was just trying to use up. The other issue was the bolt dragging in the carrier. The bolt should snap out if you flip the carrier outside the gun. If the bolt hangs in the carrier it can delay the timing of the gas to keep it from cycling fully. I didn't think it would make that much of a difference, but after a good cleaning and lube, and consistent ammo, I havn't had any problems.

 

[Greatestsin]

He took it out this week and fired off about 400 rounds of WWB 5.56 completely malfunction free. So the PMC .223 did not work well at all but the WWB 5.56 worked flawlessly. We are going to run some Federal XM193 5.56 and M85's through it this week.

 

[Litlratt]

Sounds like the PMC wasn't generating enough gas to operate it.
However, too much pressure can also cause an AR to short cycle.