Hi I am new to the forum. My son has an MP15-22. a few weeks ago he stopped by my house and grabbed a 525 round box of Federal .22LR ammo to shoot with his friends. Later in the week he had mentioned that he had a lot of misfires. When looking at the unfired round he said it looked as if the hammer did not strike the round hard enough to set it off. He said this was the 1st time he had this happen. Could it have been the ammo? He said one of the other guys fired some in his rifle without issue.

Thanks in Advance for your ideas and input

If the problem just started check for broken firing pin, broken hammer spring or hammer pin drifting out of place.

If they are all good, give the chamber a good cleaning.

Does it have the factory trigger? If not, not all drop-in triggers will strike hard enough to ignite rimfire rounds.

If it has the stock trigger group but has been disassembled at some point, there is a possibility that the hammer spring is upside-down, which will still allow the hammer to fall but with less force.

Other than that, I concur with everything already mentioned above.

First thing I would do is clean the chamber/barrel, and the bolt/firing pin channel real well. Wipe down the inside of the upper and use a good lubricant to lube the inside of the upper and bolt. MAKE SURE THE FIRING PIN CHANNEL IS CLEAN OF ALL GUNK AND DRY. DO NOT LUBE THE FIRING PIN/CHANNEL.

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SIC SEMPER TYRANNIS

The gun might need a good cleaning . Lots of new shooters like to shoot but not clean and 22 LR's semi-auto's get grungy and the crud leads to failure to fire's .
I've fixed more "broken" 22's by simply cleaning them than you can shake a stick at . Clean that puppy and try again .
Gary

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NRA Member

Thanks, everyone. I can only assume he cleaned it. LOL But I will have him bring it to the house and do a good teardown and clean.

mine used to go full auto. Lol

When I first bought mine it started to go full auto after firing the first 100 rds. It turned out the trigger pins were starting to come out. I didn't notice it at first, until I opened it up to examine it. I reseated the pins and it started to work properly.