Bolt won't turn into barrel extension.

[bb223]

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.

Gas block pinning is what they messed up initially. But it was "their" barrel and a BCM GB I purchased from them and I added the "pinning service fee" option to the order so basically I would have a barrel with a pinned GB right out of the shipping box.

I really doubt they manufacture the barrel in house but they are a "house brand" exclusive barrel they offer. It's really mind boggling as they are a major dealer in the world of AR stuff, I do not know how the first (badly pinned) barrel was headspace/bolt lock up wise as I packed it up 20 minutes after unpacking it. I just think it's a serious run of bad luck on my part because I can't imagine they're constantly putting out lemons like this.

[Stickman]

Why not send it back and tell them you need a bolt which will headspace as the ones you have on hand don't fit. If they have a bolt that fits, great. However, if they don't, it puts it right back on them.

[bb223]

Why not send it back and tell them you need a bolt which will headspace as the ones you have on hand don't fit. If they have a bolt that fits, great. However, if they don't, it puts it right back on them.

For once I can’t wait until Monday, haha. I will see what they have to say and what my options are.

However I don’t think this is simply a matter of matching a bolt to barrel to get ideal headspace. This is more of an issue of the barrel being manufactured majorly wrong as not one of the half dozen bolts I’ve tried even begins to rotate into the receiver extension, mind you this is on an empty chamber as well. I haven’t tried with live or dummy rounds or any kind of gauge.

I’m sure something can be done that would involve filing the back of each bolt lug but that’s kinda whacky to me.

[Stickman]

For once I can’t wait until Monday, haha. I will see what they have to say and what my options are.

However I don’t think this is simply a matter of matching a bolt to barrel to get ideal headspace. This is more of an issue of the barrel being manufactured majorly wrong as not one of the half dozen bolts I’ve tried even begins to rotate into the receiver extension, mind you this is on an empty chamber as well. I haven’t tried with live or dummy rounds or any kind of gauge.

I’m sure something can be done that would involve filing the back of each bolt lug but that’s kinda whacky to me.

Either is fine, but you have to send it back either way. Please don't break out the dremel and fix it yourself...

[Disciple]

However I don’t think this is simply a matter of matching a bolt to barrel to get ideal headspace. This is more of an issue of the barrel being manufactured majorly wrong as not one of the half dozen bolts I’ve tried even begins to rotate into the receiver extension, mind you this is on an empty chamber as well. I haven’t tried with live or dummy rounds or any kind of gauge.

No way would I accept them munging some bolt to fit as a fix.

[constructor]

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.

It should have .287" from front of ext lugs to breech, .277" for the lugs and .010" gap so something is off .010" at least. Measuring that accurately is a different story.

[lysander]

It should have .287" from front of ext lugs to breech, .277" for the lugs and .010" gap so something is off .010" at least. Measuring that accurately is a different story.

Where did you get your numbers?

All of the drawings give 0.283 +.006" after torquing for the gaging dimension.

The gage measurement is 0.282 +.0002.

The length of the bolt lugs is only 0.278+/- .002.

To measure, you really need the gage. But, for a good estimate: .take a depth micrometer or some dial calipers and drop the depth extension between the lugs and get the distance from the back face of the extension to the back face of the barrel,you should get around 0.209 to 0.220"

[constructor]

Where did you get your numbers?

All of the drawings give 0.283 +.006" after torquing for the gaging dimension.

The gage measurement is 0.282 +.0002.

The length of the bolt lugs is only 0.278+/- .002.

To measure, you really need the gage. But, for a good estimate: .take a depth micrometer or some dial calipers and drop the depth extension between the lugs and get the distance from the back face of the extension to the back face of the barrel,you should get around 0.209 to 0.220"

Out of my head from memory of actually machining the parts, and it does not include stretch. The bolt lugs should be .277, the extension depth .907, shank on barrel .625".
We made apx 300 bolts and extensions a week for 9 years, you are saying .289 and" I'm saying .287" that is .002" difference(apx half as thick as a piece of copy paper). It also depends on if the manufacture wants to set headspace to the middle of spec or toward the small end. We weren't building mil spec rifles for the military to eat ammo with sand on it and since most factory ammo is well under the SAAMI minimum spec we chose to target closer to minimum headspace to increase accuracy.

[lysander]

Out of my head from memory of actually machining the parts, and it does not include stretch. The bolt lugs should be .277, the extension depth .907, shank on barrel .625".
We made apx 300 bolts and extensions a week for 9 years, you are saying .289 and" I'm saying .287" that is .002" difference(apx half as thick as a piece of copy paper). It also depends on if the manufacture wants to set headspace to the middle of spec or toward the small end. We weren't building mil spec rifles for the military to eat ammo with sand on it and since most factory ammo is well under the SAAMI minimum spec we chose to target closer to minimum headspace to increase accuracy.

Well, in this case, 0.002" is the difference between fitting and not fitting.

If his bolt is not turning, and it is the extension, the distance must be something below 0.283".

Regardless of the desired headspace, the length of the lug has to be less than the gap between the face of the breech and the inside face of the extension.

[constructor]

Well, in this case, 0.002" is the difference between fitting and not fitting.

If his bolt is not turning, and it is the extension, the distance must be something below 0.283".

Regardless of the desired headspace, the length of the lug has to be less than the gap between the face of the breech and the inside face of the extension.

.
No joke, you're a smart one.
How much too small is the space between his ext lugs and breech since he has not had any way to measure it? How do you know .002" is the difference between fitting and not.
I said if his bolt lugs are.277 then the space between his lugs and breech is apx .010" too small not .002".
It could be the shank on the barrel is too long or the depth of the extension too short. Either way it's off by apx .010"
If his bolt lugs are .277" and it isn't turning then the distance between the ext lugs and breech is less than .277" or his extractor is protruding out in front of the bolt face.