AR15 Trouble Shoot

[democracywins]

I've built dozens and dozens over the years and I have a new issue that I've never experienced...

When I fire a round. It fires. It ejects. It chambers the new round. But the hammer doesn't set. I took the entire trigger group out and put it back in. All springs and everything are where they are supposed to be. Are my springs too stiff that the bolt isn't resetting it?

And it's not an upper issue. Took the upper off and ran it on another lower and had zero issues.

 

[wsenefeld]

Your disconnector isn't holding on to the hammer which is allowing it to ride home with the bcg.

Take your lower apart from your upper. Hold the hammer and squeeze the trigger to gently let it dry fire. Now, while keeping the trigger depressed, try to reset the hammer. The hammer should reset even while you keep squeezing the trigger.

If you'd like to do this with the upper on the rifle...
Remove the magazine and clear the chamber. Dry fire the rifle and continue to squeeze the trigger. Now, cycle the bcg with the charging handle until you hear the hammer reset. It should be very pronounced click. If you don't hear this...

Ensure your disconnector spring is installed fat side down. Ensure your trigger spring loop is under the front notch of your trigger.

If both of those are correct, loosen your pistol grip screw 1 full turn and try again.

 

[Jeremy1066]

And report back to acknowledge wsenefeld's awesomeness!

 

[wsenefeld]

Some other ideas until the OP reports back...

An 80% lower that wasn't finished properly

A fire control group that is out of spec. Try the problem fcg in a lower that you know works. Then if the fcg works you might check to see if the lower is out of spec. Or try a functioning fcg in this lower. If it works, it was the trigger if it doesnt, again, it's an out of spec lower.

Maybe a trigger/disconnector from one kit and a hammer from another kit?

 

[democracywins]

Thank you for the info. Tried everything in the first post last night and still getting the same result. I honestly now believe it the fcg is out of spec, however I will confirm tonight as I will take it out and put it in another lower I know works. Thanks again!

 

[Grease]

Same thing happened to me on my wife's Colt. Ended up replacing the FCG and all is fine now.

 

[DanVoils]

Happy you got it figured out. It would be interesting to troubleshoot it down to a particular part. I'm curious which one is at fault.

 

[jblomenberg16]

What kind of lower? I bought a cheap plastic ATI lower a few years ago to mess around with. Trigger pin hole spacing was out of spec and it did the same thing.

 

[Inabcentia]

Hey Democracy Wins, any news to report? Very curious what you discovered. I am with Dan Voils and would like to know if you could home it down to a single part.