Bad AR15 bolt?

[jkgts1]

Sorry wrong section can admin please move?

Hey guys and gals. Anyone ever had a bad bolt that would not allow their rifle to chamber a round? My friend just built his AR and took it to the range and it would not chamber any rounds. It would strip the round from the mag but would bind with the round half way into the chamber. I'm not sure all the specs of his rifle, 5.56, 18", rifle length gas system, everything else is pretty standard. Anyway I got home and switched parts around with my AR and found it is the bolt itself. Not the bolt carrier group, but just the bolt. Put his bolt in my carrier and my rifle had the same malfunction. I cannot tell with the naked eye what is wrong with his bolt but it's doing something wrong. Any thoughts?

[ar15barrels]

I have seen many bolts that were short on headspace due to plating.
This is because the companies took a standard dimension bolt, then plated it.
The plating shortens headspace by double the thickness of the plating as there are two dimension critical surfaces that get material deposited on them.

The RIGHT way to do a plated bolt is to make it purposely LONG on the headspace dimension by twice the plating thickness.
That way, the bolt will come INTO spec after plating instead of going OUT of spec.

[bohoki]

a bind halfway into the chamber is not a headspace issue it sounds like a mag problem the lips sound too low and it is possibly damaging the casing or bending the bullet during the feed

[Thorax]

Or the bolt is not moving in the carrier easily enough to lock/unlock.

Scrub and grease well....try it again.

[baih777]

Take the bolt apart and inspect it. It may have just been assembled incorrectly.
Make sure the plunger and the shell extractor are working correctly.

[jkgts1]

Thanks for replies. I know it's not mags, because that mag works in my other ARs. I'm sure it's a bolt issue, because that is the only part that changed on the rifles. The problem moved from rifle to rifle and that bolt. It is a coated bolt. Friend said it's a complete bolt carrier group from Rock River. Just kind of weird for me because I've never had one of my bolts do that.

[bohoki]

Thanks for replies. I know it's not mags, because that mag works in my other ARs. I'm sure it's a bolt issue, because that is the only part that changed on the rifles. The problem moved from rifle to rifle and that bolt. It is a coated bolt. Friend said it's a complete bolt carrier group from Rock River. Just kind of weird for me because I've never had one of my bolts do that.

i have an all chrome rock river and it works fine guess its a bad part then if you narrowed it down with known good

have you tried that bolt in a non coated carrier cause i did run into a similar problem with a nickelboron bolt that would not work in its carrier or my colt carrier but it would work in a p-tac carrier it just felt like there was resistance

so i did some shuffling and the nickle boron bolt works great in my pistol with the non coated carrier and the non coated p-tac bolt with slightly weak extractor spring works fine in a rifle with the nickel carrier

[kendog4570]

Check your extractorEJECTOR length and stickout from the bolt front. It should be slightly recessed. An out of spec extractorEJECTOR or out of spec extractor EJECTOR retaining pin hole in the bolt will allow the extractorEJECTOR to protrude in front of the bolt and cause a feed jam every time. Stupid stuff like this has become common since everybody and their uncle have been making AR parts since 2002. Some really good, some not so good.


Fixed it as I am a dumb azz and cant think and spell at the same time!

[jkgts1]

i have an all chrome rock river and it works fine guess its a bad part then if you narrowed it down with known good

have you tried that bolt in a non coated carrier cause i did run into a similar problem with a nickelboron bolt that would not work in its carrier or my colt carrier but it would work in a p-tac carrier it just felt like there was resistance

so i did some shuffling and the nickle boron bolt works great in my pistol with the non coated carrier and the non coated p-tac bolt with slightly weak extractor spring works fine in a rifle with the nickel carrier

Yep
Coated bolt + non coated carrier= malfunction
Non coated bolt +coated carrier= no malfunction
Coated bolt +coated carrier (in different upper and lower)= malfunction
Uncoated bolt + uncoated carrier (in different upper and lower) = no malfunction

[jkgts1]

Check your extractor length and stickout from the bolt front. It should be slightly recessed. An out of spec extractor or out of spec extractor retaining pin hole in the bolt will allow the extractor to protrude in front of the bolt and cause a feed jam every time. Stupid stuff like this has become common since everybody and their uncle have been making AR parts since 2002. Some really good, some not so good.

Okay I'll take a look at that, thanks.

[ar15barrels]

Check your extractor length and stickout from the bolt front. It should be slightly recessed. An out of spec extractor or out of spec extractor retaining pin hole in the bolt will allow the extractor to protrude in front of the bolt and cause a feed jam every time.

Such a clearance problem should show up without a cartridge as well.
I have not run into this problem yet.
When I run into failures to breech on AR's, it has usually been short headspace caused by plating stack-up.

The typical clearance between the front face of the bolt lugs and the breech of the barrel is usually 0.012" to 0.015" in most AR barrels.
Have you observed more protrusion of the extractor from the bolt lugs face than that?

[kendog4570]

Such a clearance problem should show up without a cartridge as well.
I have not run into this problem yet.
When I run into failures to breech on AR's, it has usually been short headspace caused by plating stack-up.

The typical clearance between the front face of the bolt lugs and the breech of the barrel is usually 0.012" to 0.015" in most AR barrels.
Have you observed more protrusion of the extractor from the bolt lugs face than that?

I MEANT ejector and NOT extractor. My Bad. Sux getting old.

The OP's jam is with the round halfway in. That is a lot of head space. If ejector is proud of the bolt face even by a few thousandths, the base of the cartridge will hang right there as it clears the mag lips. The last on I dealt with was about .010. I didn't measure it. The case was toggled between the extractor, ejector, and the mouth of the chamber. Putting a correct ejector in and problem went away

[kendog4570]

Such a clearance problem should show up without a cartridge as well.
I have not run into this problem yet.
When I run into failures to breech on AR's, it has usually been short headspace caused by plating stack-up.

The typical clearance between the front face of the bolt lugs and the breech of the barrel is usually 0.012" to 0.015" in most AR barrels.
Have you observed more protrusion of the extractor from the bolt lugs face than that?

My Bad. I meant ejector, not extractor. I think it's oldtimers disease setting in!

[jkgts1]

Well my friend stopped by, picked up his rifle, bolt, and did not get a chance to measure. He said he will call Rock River about the part. Thanks for all the help. I really was just curious to see what was causing this.