Sticky AR bolt....

[TooTallMike]

Also consider stripping it and seeing if the carrier itself will slide freely into the upper. Then try it with the charging handle and if they do then it narrows it down to the cam pin and bolt.

Just two days ago I fixed a jacked looking carrier that had LOTS of resistance going through the upper. Turns out it was the staking on the gas key that was causing the while issue. Dremel and 8 seconds on each side and that bad boy was butter.

[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.

and there are the terms I was fishing for ealier

I'll gladly offer the correct terms when I can. I just appreciate your builds and the INSANE performance of them.

Keep it up 👍

[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

I'll gladly offer the correct terms when I can. I just appreciate your builds and the INSANE performance of them.

Keep it up 👍

thank you. Will do

[lokidog]

Also consider stripping it and seeing if the carrier itself will slide freely into the upper. Then try it with the charging handle and if they do then it narrows it down to the cam pin and bolt.

Just two days ago I fixed a jacked looking carrier that had LOTS of resistance going through the upper. Turns out it was the staking on the gas key that was causing the while issue. Dremel and 8 seconds on each side and that bad boy was butter.

The bolt assembly falls into the upper easily and closes easily with no cartridge. It is only when a cartridge is involved that there is an issue.

[NitRally]

Check the gas rings. The three tiny washers on the end of the bolt make sure all the spaces are equally separated.

[NitRally]

Had a similar problem, the rings were getting bound in the carrier. Hope this helps. (If they're mangaled they're like 5 bucks for all 3.)

[JimmyHoffa]

Ammo?
One time, back when I was slightly more of a moron, I didn't fully resize a batch of cases.  The die was just a hair to high, but length was good.  The shoulder was a bit of an issue and was giving problems when trying to send the bolt home.

[lokidog]

Ammo?
One time, back when I was slightly more of a moron, I didn't fully resize a batch of cases.  The die was just a hair to high, but length was good.  The shoulder was a bit of an issue and was giving problems when trying to send the bolt home.

Factory

Also consider stripping it and seeing if the carrier itself will slide freely into the upper. Then try it with the charging handle and if they do then it narrows it down to the cam pin and bolt.

Just two days ago I fixed a jacked looking carrier that had LOTS of resistance going through the upper. Turns out it was the staking on the gas key that was causing the while issue. Dremel and 8 seconds on each side and that bad boy was butter.

I'm thinking cam pin at this point and will take a look at my friend's bolt assembly in a day or two. The cam pin does seem to slide and rotate more easily on the "working" one.

[Yondering]

The bolt assembly falls into the upper easily and closes easily with no cartridge. It is only when a cartridge is involved that there is an issue.

That would have been a good detail to include in the first post. Way too much of this thread is just guessing without enough info, as is typical of internet problem diagnostics.

If the problem only happens when a cartridge is in the chamber, then it has nothing to do with the gas rings, cam pin, gas key, etc or any of that stuff. You've either got an extractor problem, or something causing the ammo to not fit the chamber (this is the most likely).

Did you switch ammo? Are these reloads? Is the chamber dirty?
Figuring out why your ammo doesn't fit the chamber is the first step. I wouldn't bother with any of the other things suggested here until you do that.

If it's not anything obvious, you can color a cartridge with a sharpie marker (color the entire case and the bullet), then try to chamber it, and look where the sharpie rubbed off. Some scratches on the case neck and bullet are normal from extracting a live round; you're looking for some sort of rub mark or maybe a ring that goes all the way around the case or bullet.

Hope that gets you started in the right direction.

[dreadi]

Has it been determined that the bolt is the correct bolt for the caliber of the gun?

[lokidog]

Has it been determined that the bolt is the correct bolt for the caliber of the gun?

Yes

The bolt assembly falls into the upper easily and closes easily with no cartridge. It is only when a cartridge is involved that there is an issue.

That would have been a good detail to include in the first post. Way too much of this thread is just guessing without enough info, as is typical of internet problem diagnostics.

If the problem only happens when a cartridge is in the chamber, then it has nothing to do with the gas rings, cam pin, gas key, etc or any of that stuff. You've either got an extractor problem, or something causing the ammo to not fit the chamber (this is the most likely).

Did you switch ammo? Are these reloads? Is the chamber dirty?
Figuring out why your ammo doesn't fit the chamber is the first step. I wouldn't bother with any of the other things suggested here until you do that.

If it's not anything obvious, you can color a cartridge with a sharpie marker (color the entire case and the bullet), then try to chamber it, and look where the sharpie rubbed off. Some scratches on the case neck and bullet are normal from extracting a live round; you're looking for some sort of rub mark or maybe a ring that goes all the way around the case or bullet.

Hope that gets you started in the right direction.

Don't know what to tell without someone asking. ;-)

There is some odd wear on the cam pin corner that turns into the receiver, see pic.

HOWEVER, with a little more research on my "friend's" gun, it turns out to only happen with the HexMags and not the PMags in both receivers. I dug out the micrometer and there are slight differences in dimensions on various parts of the bolt body.

The "sticky" bolt works with the PMags in both receivers. I found someone that sanded the top edge down a little so decided to try that, seems to be getting better as I shave the top down slightly.

Thanks everyone for the suggestions.

[lokidog]

So, I reshaped the front of one of the magazines to look more like the PMag. It was a little better, but not a lot. I then noticed that the magazine popped in easily with the bolt open but not so easily with it closed so I shaved the highest point down just slightly and... voila. It cycles nicely now.

I'm still curious about the wear in the previous photo though.

[TooTallMike]

What upper is it running?

Have you inspected the inside of the upper?

[lokidog]

What upper is it running?

Have you inspected the inside of the upper?

It behaves the same in both uppers that my friend has....

One upper was a build project, don't remember the bolt or upper maufacturer. That one works with both unmodified magazines. The other is an upper from 22modsforall. That is the one with the issues with the HexMag, and the bolt has those issues in both of the uppers.

There are other people on the internet that have had this issue with the HexMag (gen 2).

[Yondering]

Has it been determined that the bolt is the correct bolt for the caliber of the gun?

Yes

The bolt assembly falls into the upper easily and closes easily with no cartridge. It is only when a cartridge is involved that there is an issue.

That would have been a good detail to include in the first post. Way too much of this thread is just guessing without enough info, as is typical of internet problem diagnostics.

If the problem only happens when a cartridge is in the chamber, then it has nothing to do with the gas rings, cam pin, gas key, etc or any of that stuff. You've either got an extractor problem, or something causing the ammo to not fit the chamber (this is the most likely).

Did you switch ammo? Are these reloads? Is the chamber dirty?
Figuring out why your ammo doesn't fit the chamber is the first step. I wouldn't bother with any of the other things suggested here until you do that.

If it's not anything obvious, you can color a cartridge with a sharpie marker (color the entire case and the bullet), then try to chamber it, and look where the sharpie rubbed off. Some scratches on the case neck and bullet are normal from extracting a live round; you're looking for some sort of rub mark or maybe a ring that goes all the way around the case or bullet.

Hope that gets you started in the right direction.

Don't know what to tell without someone asking. ;-)

There is some odd wear on the cam pin corner that turns into the receiver, see pic.

HOWEVER, with a little more research on my "friend's" gun, it turns out to only happen with the HexMags and not the PMags in both receivers. I dug out the micrometer and there are slight differences in dimensions on various parts of the bolt body.

The "sticky" bolt works with the PMags in both receivers. I found someone that sanded the top edge down a little so decided to try that, seems to be getting better as I shave the top down slightly.

Thanks everyone for the suggestions.

OK, so that's different again from what you said. It sounds like the issue is when a magazine is in the gun, not necessarily when a cartridge is in the chamber. That points to a magazine issue, as you said. It's hard to give accurate suggestions without the correct info. On the flip side of that, beware of people who do give suggestions without having much info; they're probably guessing just as much as you are.

Glad you got it figured out.