AR15 not cycling - Smith and Wessons M&P Sport II

[Boris]

Hi all gun people, hope everyone is doing well.

I've got an issue with a Smith & Wesson M&P Sport II 223 rifle, maybe someone can assist. Please excuse if I'm posting in the wrong area.

So it's a new gun, not even 300 rounds through it. The shop where I got the gun, fitted for me a new gas block and free float rail. A UTG non adjustable micro gas block and a DM free float rail. (I think it's a DM)

Long story short, I got a silencer and really started noticing the issue, gun would jam 3 out of 5 rounds about. It doesn't cycle properly.

Eventually sold the silencer and just stuck with the standard A2 cage. Still not cycling properly and with further testing it seems the gun doesn't lock back at all. I can pull the CH back and it locks just fine, but not on it's own and this is obviously causing the jams.

About a week ago I bought a superlative arms adjustable gas block. Seems to be a good product as far as I could find. This was installed and here is how it went.

I started with the port closed, as suggested in the instructions. Gun fires fine, but obviously doesn't eject the casing. Adjusted in clicks up until it ejects casings between 3:30-4:00. So it would seem the gas system is function properly in that sense. I even went up higher with clicks up until it didn't eject anymore. The superlative arms gas block has a "bleed off" function where it lets gas out the front when opened too much, if I understand correctly. So ja all in all, gas seems to be functioning correctly.

However the bolt is not catching. I was shooting one round at a time, with different brand magazines for reference sake.

If it would help, what I'm shooting:

Vihtavuori powder (24gr)
random once fired brass
winchester 55g bullets
cci primers
about 3000 through the chrony

The same issue occurs with factory ammo.


I'm out of ideas, possibly something with the buffer spring? Anyone has some ideas or suggestions perhaps?

[Rigby]

begin with factory ammo to rule out the possibility of reloading error .

[Boris]

The same thing happens with factory ammo.

[thomasnels]

When i had issues a few years ago with cycling it was my bolt carrier group gas key that was loose and not torqued according to spec and not properly staked (Leaking). If in Pta speak to Gerhard at Hailstorm he will be able to sort it for you

[Boris]

Thanks for the tip. I'm in the western cape though.

[Rigby]

The same thing happens with factory ammo.

noted

[Skip]

I have to full size my brass for the S&W - not just neck size

[Boris]

Thanks yes I full size all my brass. Except for the gas key possibility, what other suggestions do you guys have. Could it possibly be something wrong with the buffer spring?

[FNBROWNING]

Thanks yes I full size all my brass. Except for the gas key possibility, what other suggestions do you guys have. Could it possibly be something wrong with the buffer spring?

Does it lock back if you manually pull the charging handle back. Is there possibly too much play in the bolt catch. Sometimes magwell or catch cut are out of specspec.But if activates manually then likely not that.The fact that you have changed the gas block sais that you look at this first. Is it leaking gas,is it blocking the port slightly. Is the gas tube correct. Is the gas tube canted. Buffer spring in commercial rifles is unlikely to be an issue. If anything the can be a tad soft allowing higher bolt speeds but if bad enough to catch that would give bolt over base failure.

[Ωhm]

[QUOTE=Boris;1516174Anyone has some ideas or suggestions perhaps?[/QUOTE]

Describe the jam, or even better, provide pictures. There are many things from the end of the buffer tube to the gas block, that can cause an AR15 to not cycle correctly.