Sticky AR bolt....

[lokidog]

Not saying that I own an AR, but, for a friend....

Any suggestions on what to check for with a sticky bolt? My "friend" has a newer, slightly used upper, 50-100 rounds through it, that won't close all of the way. The bolt was tried in an upper that functions fine and stuck about 1/4 inch short of closing every time it was cycled.

It was cleaned after shooting the last time.

TIA

[Dan-o]

This also happened to a "friend" I know.   
Exact same symptoms.

When I.....    I mean when my friend finally throughly disassembled it, I found a small piece of brass jammed toward the front of the bolt.

I would thoroughly disassemble your friends AR.       

[jasnt]

I’d pull the bolt and inspect lugs and pin groove that allows the lugs to lock. Also check the gas piston thingy can’t think of the proper term.  Make sure those screws are tight. Make sure the lugs turn smoothly as they cycle back

[fishngamereaper]

Cleaned as in sprayed and wiped down or complete disassembly of BCG, bolt, etc... sounds like the bolt won't rotate and lock into the lugs.

Empty chamber or loaded?

[fishngamereaper]

Also can you send it home with forward assist or does it stop...

[Alchase]

This also happened to a "friend" I know.   
Exact same symptoms.

When I.....    I mean when my friend finally throughly disassembled it, I found a small piece of brass jammed toward the front of the bolt.

I would thoroughly disassemble your friends AR.       

That or a primer

[Jingles]

Experienced a similar problem recommend disassembling the BCG and thoroughly cleaning  possibly something keeping it from completely seating.

[TooTallMike]

Check your gas key and make sure it's not loose or marred up causing the carrier to hit the gas tube.

Then look at the cam pin. Had a similar issue once and it was a defect from the factory. Swapped it out and worked fine.

Finally check your lugs and disassemble as everyone else said.

Hope you get your "friends" gun up and running.

[jasnt]

Check your gas key and make sure it's not loose or marred up causing the carrier to hit the gas tube.

Then look at the cam pin. Had a similar issue once and it was a defect from the factory. Swapped it out and worked fine.

Finally check your lugs and disassemble as everyone else said.

Hope you get your "friends" gun up and running.

and there are the terms I was fishing for ealier

[lokidog]

It worked the last time I shot it. I did not disassemble the bolt for cleaning.

There are no marks or mars except maybe a little rub on the rear left corner of the bolt cam pin.

It will close using the forward assist.

When moving the bolt assembly into the carrier, there is some resistance as the bolt cam rotates back.

All screws seem tight.

I put this, I mean my friend put this bolt in another upper and it actually stuck shut.

I'd post photos but I moved locations and did not take his bolt with me. I might have access to it after Tuesday. 

Thanks everyone for the input.

[JimmyHoffa]

I'll also add cleaning the BCG.  I've had a few instances of the sticky bolt, especially when it is still cold.  Spraying WD40 didn't loosen it or trying to cycle by hand.  Had to clean all that carbon off in the bolt.

[fishngamereaper]

Strip it down and clean it good. Problem solved.

Some powders will actually mix with some cleaners and a chemical reaction creates a solid..I've dug some nasty stuff out of BCGs.

[lokidog]

Strip it down and clean it good. Problem solved.

Some powders will actually mix with some cleaners and a chemical reaction creates a solid..I've dug some nasty stuff out of BCGs.

Wish I had taken a photo, it is pretty darn clean.

[Dan-o]

Strip it down and clean it good. Problem solved.

Some powders will actually mix with some cleaners and a chemical reaction creates a solid..I've dug some nasty stuff out of BCGs.

Wish I had taken a photo, it is pretty darn clean.

Good to know your friend cleaned it well.

I'd still take the BCG down to parts and clean it.

That has also been a cause for my friends' AR sticking in the past.

[lokidog]

He might try buffing the bolt cam a bit.