Bolt won't turn into barrel extension.

[bb223]

Brand new barrel that was actually a replacement barrel from a company I ordered a barrel from that they botched the taper pin job on.

Waited over 3 weeks for it to come and was 100% happy with how they pinned the LPGB to it, went ahead and got the barrel inserted into the BCM upper ahead of time because I was going to take it and install the barrel nut and rail to my buddy's tomorrow (I don't have a torque wrench, he does though )

Anyway I bought a brand new AO Precision "milspec" BCG to use on this build and figured I would just slide it in the upper to see how it fit and this is where the trouble began.

The BCG didn't go in all the way and I tried tapping it with the heel of my hand and it didn't move, thinking it was the BCG that was the issue I tried the BCG out of my 6920 and that didn't fit, neither did the PSA bolt or the Toolcraft bolt either.

So then I went and took the bolts themselves out of the carrier and I could not get any of them to rotate in, so then I went through the "fun" process of heating the upper back up and knocking the barrel out of it with a dowel rod so I could see the chamber up close and I saw nothing at all wrong with it, no burrs or dirt.

Tried cleaning it and still no bolts fit.

So I guess I'll have to send this barrel back too?

Is there possibly some fix I'm overlooking?

To clarify every other bolt will drop and spin freely into every other rifle I own, I'm kind of thinking maybe the company who sold the barrel has the barrel extension turned in too much so it's now too tight for the bolt to spin? Every bolt head drops in perfect and below the barrel extension lugs but not a single one of them even begin to spin.

Pics:

[georgeib]

The only reasonable fix is a replacement barrel.

Who is the manufacturer?

[bb223]

The only reasonable fix is a replacement barrel.

Who is the manufacturer?

Damn. I'm not 100% sure how the extensions work but I was hoping maybe it would be as simple as them unscrewing the old one and maybe machining a bit off and reinstalling.

I have emailed them and they haven't replied yet I do not want to violate TOS by mentioning who they are.

[1168]

If the Colt bolt won’t fit……

[bb223]

If the Colt bolt won’t fit……

Especially considering this particular Colt bolt has 35,000 rounds on it...

[Todd.K]

A barrel has to be made with the correct distance between the shoulder and the breechface. A barrel extension has to have the correct distance from the back to the lugs inside. Both are supposed to be held to VERY tight tolerances. This allows the correct clearance for the bolt lugs.

Make sure the there is nothing from shipping or manufacturing inside the barrel extension area, other than that there is no “fixing” it.

[constructor]

A barrel has to be made with the correct distance between the shoulder and the breechface. A barrel extension has to have the correct distance from the back to the lugs inside. Both are supposed to be held to VERY tight tolerances. This allows the correct clearance for the bolt lugs.

Make sure the there is nothing from shipping or manufacturing inside the barrel extension area, other than that there is no “fixing” it.

Depends on what is wrong.
If the extension is shallow it can be removed and tossed, replaced with one that times close to zero, then face the extension (a few thou max)so it does time to zero and aligns with the gas port.
If it is a nitride treated barrel and the shank on the barrel is long you could face the breech if only off a few thou. It just depends on how much time you want to put into it, what is acceptable and if you have the means to do it.
ETA- Personally I would ask for a refund and look for a brand that does not use Nitride treated barrel extensions.

[bb223]

A barrel has to be made with the correct distance between the shoulder and the breechface. A barrel extension has to have the correct distance from the back to the lugs inside. Both are supposed to be held to VERY tight tolerances. This allows the correct clearance for the bolt lugs.

Make sure the there is nothing from shipping or manufacturing inside the barrel extension area, other than that there is no “fixing” it.

Yeah, I looked at it from every possible angle and used those goofy "star chamber cleaning swabs" and everything and didn't notice anything abnormal save for what appears to be a visible female thread from the receiver extension, I've never seen this before in any barrel but I don't know if it is indicative of anything.



I wish I had a way to measure the gap between the extension lugs and the barrel face and compare it to known good barrels but my calipers don't fit in any of my assembled uppers and I'm not trying to dissemble any known good working stuff.

[bb223]

ETA- Personally I would ask for a refund and look for a brand that does not use Nitride treated barrel extensions.

It's really funny how the barrel was the only thing I was sure and excited about and essentially built the rifle around it and its configuration, and it ended up being the only thing that didn't go smoothly at all.

This was the first barrel I bought from the company that shipped 6/12 and I paid extra to have the BCM LPGB pinned to the barrel, it arrived looking like this.



They acknowledged it was done wrong and immediately sent a return shipping label and over 3 weeks later its replacement came and the pin job was absolutely perfect but as you can see the headspace/bolt lock up/whatever is unsat.

[grizzman]

It seems defective to me, and needs to go back to the manufacturer.

Did the barrel manufacturer screw up the P/W task? If so, then I agree with Constructor, and a refund (and a different barrel manufacturer) would be chosen.