I've built a few uppers and lowers from parts and it has always worked great.  However, I've just received a used barrel in 6x45mm that I wanted to use just to try out this round and there is too little space between the barrel chamber face and the front of the locking lugs.  As a result a bolt will not close in it.  I've tried two used and two new bolts (Colt, RRA, RRA, unknown) and none will close though the used RRA one almost does but it takes enough force that it would never work in an assembled rifle.  Is there a simple means to fix this or is this barrel fubar?  It was cheap but I'm getting a feeling that I know why it was cheap now.

Defective barrel.  

And headspace, etc is not adjusted by how much torque on the barrel extension.  

Your barrel was not machined correctly.  You got taken.

Quoted: .... You got taken.

Maybe not...

If you don't mind wasting a bolt to find out, take the one that's closest to fitting and place a piece of 400 Emery cloth on a flat surface. Hold the bolt flat face down and move it around in a figure 8 fashion until it fits.  If you're that close with one bolt it might work.  Of course once the bolt fits check for chamber fit.  If you reload just fire form your brass, measure OAL with a guage and size and load accordingly.

Maybe you got the barrel I sold a few years ago. It was purposely short chambered to accomodate the loaded round I wanted. All you need to do is set your size die to bump the shoulder back a little, check the case OAL and trim as req.  Or just have the chamber deepened.  Make a cerrosafe cast of the chamber so you know what you are dealing with.

Removing material from the front of the bolt will not solve short headspace. Material would have to be removed from the back of the lugs. Really not a good idea.
If the barrel isn't chromed, have the chamber recut.
Or as already stated, handload for it and bump the shoulder back.


mark

double tap

I think that I will not remove any material from the bolt though I've given it some thought.  Really the bam extension will have to be reinstalled and the barrel rechambered to properly correct this or at least that is my feeling at this time.  I've called the shop that sold it to me and have asked them to take care of it as they said it was ready to go.  I'm waiting to hear back from them.

Quoted: I think that I will not remove any material from the bolt though I've given it some thought.  Really the bam extension will have to be reinstalled and the barrel rechambered to properly correct this or at least that is my feeling at this time.  I've called the shop that sold it to me and have asked them to take care of it as they said it was ready to go.  I'm waiting to hear back from them.

Unless I'm missing something, you have to chamber with the extension on and tight, so that you can properly check you headspace depth as you chamber.  Maybe not, though.  If you had a chambering fixture and you knew exactly how deep to chamber without the extension installed, I guess that would work, but it would seem just as likely, that with tolerances in the barrel, fixture and reamer wear, you'd be just as likely to be off as you would be on.  That's just my machinist 2 cents.

Removing material from the front of the bolt will not solve short headspace. Material would have to be removed from the back of the lugs. Really not a good idea.
If the barrel isn't chromed, have the chamber recut.
Or as already stated, handload for it and bump the shoulder back.



Who said this is a headspace problem?  The bolt cannot turn in the extension.  Removing material from the front of the bolt will not change headspace.  That will only change if material is removed from the FACE of the bolt, that is, the surface that contacts the head of the cartridge, or material removed from the back of the lugs.

Right now we don't know what the headspace is.  The bolt won't close.  

"there is too little space between the barrel chamber face and the front of the locking lugs. As a result a bolt will not close in it. "

Halfcocked's suggestion would be the easiest to try first.

"Right now we don't know what the headspace is. The bolt won't close. "

Exactly.... I can't check the headspace untill I can get a bolt to fit.  I'm waiting to see if the seller can come up with the original bolt that went with this barrel right now.  It was used so there must have been a bolt that fit at somepoint.

I would say that if your bolt is contacting the barrel and not locking into the extension due to lug length being too long, you have far bigger problems than you think.  Something was not right when this build was put together and that should be fixed before you start curing symptoms and not the actual problem.  KABOOM is very possible when you start messing around in areas like this.

There should be a small, but noticable gap in the bolt lug length and extension.  I can't tell if you had tried to insert and rotate the bolt by hand, but you should try that, if you haven't already.  The bolt should insert and rotate in the extension freely.  If it doesn't stop and get professional help, as somebody made a miscalculation on something and that specific problem should be fixed before you start shaving this and that to make it work.

D'oh!  Sometimes the simple solution is the best solution... Although I had cleaned the offending area with normal means already I figured I'd give it another go with disk shaped nylon brush on a dremel tool and now three out of four bolts will close and will also close on resized brass.  The extension is still spaced rather closely to the barrel based on my experence but I now think that it will work ok.   The only bolt that is still too stiff is a no name unit that I just got the other day that has some thick looking black coating on it.  Thanks for all the ideas and such  

Quoted: Removing material from the front of the bolt will not solve short headspace. Material would have to be removed from the back of the lugs. Really not a good idea. If the barrel isn't chromed, have the chamber recut. Or as already stated, handload for it and bump the shoulder back. Who said this is a headspace problem?  The bolt cannot turn in the extension.  Removing material from the front of the bolt will not change headspace.  That will only change if material is removed from the FACE of the bolt, that is, the surface that contacts the head of the cartridge, or material removed from the back of the lugs. Right now we don't know what the headspace is.  The bolt won't close.   "there is too little space between the barrel chamber face and the front of the locking lugs. As a result a bolt will not close in it. " Halfcocked's suggestion would be the easiest to try first.

Bahhhh.... that's what I get for trying to help while I'm at work.
I didn't catch the fact there wasn't a case in the chamber.

This was one I had to read over a few times myself!

I test fired the upper today... the accuracy in nothing great (like an SKS).  Main issue now to sort out is  that it ejects the empty but the bolt is not coming far enough back to pickup a new round or to catch the bolt hold open.  The last owner had been messing around with some sort of screw in the gas block and I suspect the gas port in the barrel is too small or something like that.

Using a standard buffer spring insted of the heavy duty wolf spring has resulted in the 6x45 upper working nicely