Hope everyone is well. I have a sport II that is about 4-5 years old and only has about 250-300 rounds through it. Always ran flawless. Took it out to play yesterday, and it shot one round... then 'click'... tap-rack-bang and most of the time it would fire off a round and then the same thing would happen.

What I know:
It's not the ammo, I was using good brass and it ran fine Previously and ran fine through another AR yesterday.

I have installed an Armaspec SMB buffer, but I'm pretty sure I have ran It prior to yesterday with SMB buffer.

Only other changes I've made to this particular rifle are EP dust cover, grip, butt stock, take down pins, and hand guards.

Any ideas? Thanks in advance.

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SFMF. 🇺🇸 🦅 🌎 ⚓️🇺🇸

Couple of thoughts. Did you try a different mag? Another possibility is that the grease/oil has congealed, and it needs a good cleaning.

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Peace was my Profession

Yes sir, 3-4 diff mags.
Could that happen from sitting for a while without being fired? I always clean them when I get home from a range. However, I do remember smelling a strange smell... like ammonia.

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SFMF. 🇺🇸 🦅 🌎 ⚓️🇺🇸

Well alright. ��

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SFMF. 🇺🇸 🦅 🌎 ⚓️🇺🇸

Sorry, I just saw this.

Are you sure the BCG was fully closed when it didn't fire?

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Freedom isn't free.

Why the buffer change? Lube it up good and see what that does ,I am also thinking it is not closing bolt completely.

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Hue 68 noli me tangere

I'd question the buffer change also. Besides what Vonn noted, I'd pull the recoil spring out, clean and inspect the inside of the buffer tube/receiver extension and reassemble with the original buffer. Perhaps also pull the bolt out of the carrier and inspect the gas rings and the bolt cavity in the carrier for signs of anything suspect.

It does sound like it's either got excessive friction or you've done something to the gas system. You might check the bolts on the gas block on the carrier. They're usually staked so they won't back out, but stuff happens.

There's always the return to S&W for warranty service.

Pull the bolt carrier group, clean and lube it, then give it a try. If that doesn't fix it, remove the buffer and put the OEM buffer back in. I'd bet one of those items will cure your issue. Good luck.

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SFC, US Army, Retired

As others have said, the first thing to look at is what you have recently changed. The buffer is the only change you've mentioned that could affect function. Take it out and put the factory buffer and spring back in. Then see if it'll run. If it does you found the problem. If not it may be time to send it in for a look.

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Or something like that . . .