Very Interesting Result from Removing a Stuck Case

D

Denny Gibson

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Mar 5, 2017
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Location
Chillicothe Illinois
I recently purchased a Spanish Mauser in .308 ... or so I thought.

Shortly after receiving the rifle I took it to the range to shoot it the first time. When I tried to load a .308 cartridge I found that it was considerably larger than the space provided in the chamber. Confused and a bit perplexed I took the gun home to have a closer look. Looking closely I noticed what appeared to be an edge .060" below the chamber entrance so I thought it might be a stuck case. After trying every method I could think of to remove the case with no luck at all. I then took it to a gunsmith who tried a couple times to pull the case out with the same result. SO we decided it was time to take look in the chamber region with a lighted borescope. That's when we realized we had complete, although smaller. chamber and no stuck case. He pulled out a 7.62x39 round which chambered perfectly.

Here's the weird part: the receiver is stamped 7.62 and I plugged the bore and measured the groove diameter to be exactly .308" Why would someone create a barrel with a 7.62x39 chamber and .308 bore and groove dimensions? We know the Russian round shoots .310 - .312 30 caliber bullets or as much as .004" larger than .308 which causes an issue with reloading.

I could just shoot .308 bullets if they will fit tight enough in the case mouth. I could shoot .310" bullets and accept the high barrel temperature and faster bore wear rate; or I could ream the chamber to .308 specs. I like the idea of shooting 7.62x39 in a Mauser but I'd be fine with a .308 rifle.

Please chime in with comments and any other ideas you might have.

Thanks!
 
No real problems if reloading. But will probably be over pressure using .310 but maybe not enough to really worry about. The original Ruger Mini 30 had .308 bore. Edit: .300 bore dia .308 groove diameter.
 
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Thanks folks!

Can a finish reamer be used to shape a .308 chamber in this barrel? I’m not sure the reamer would be piloted correctly with the bore that’s there or if it even matters.
 
Denny Gibson said:
Thanks folks!

Can a finish reamer be used to shape a .308 chamber in this barrel? I’m not sure the reamer would be piloted correctly with the bore that’s there or if it even matters.
Click to expand...
A good machinist can easily do it. .308W body diameter is .473" and 7.62x39 is .447". I wouldn't try it with a finishing reamer because of the amount of material to remove, but that's outside my skill set.
 
The Spanish Mauser is chambered for the 7.62 or .308 CETME. Not sure about chamber differences, but the CETME round is a lower pressure cartridge than the .308 Winchester. Also, the small ring Mauser action is rated for lower pressures than the .308 Winchester or 7.62 Nato round. Unless this rifle was rebarreled to 7.62 x 39, you are likely to get a ruptured case or worse. Do not shoot 7.62 x 39 in this rifle.
 
I'm curious to see the bolt face and the work that went into it to take a smaller rim diameter cartridge. Pictures please. There is a big difference in the rim diameter between the 7.62x39mm and the 7.62x51mm.

Jeremy
 
I have the same rifle and it sounds like someone put a 7,62x39 chamber adapter in it. I had one in mine for awhile. It worked very well. Cartridges would feed if you were careful and eject fine. Prety accurate also. It was loctited in. After about 500 rounds chambering a round started getting tight. I figured the adapter might have been shifting so I removed it. IIRC the adapter was from Ace Dube. It came with it,s own loctite so I,m not sure which. I had to heat the chamber area with a heat gun to soften the locktite and use a stuck case remover to pull it out. It got chipped around the mouth so I never put it back in. If it works ok I,d leave it. Good luck.
 
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SC45 I get what you're saing but I don't really see the point. The CETME cartridge is virtually identical to 7.62 NATO anad .308 Win. The danger that someone might overload it will always exist whether I make it a .308 or it started off that way,
 
So ... I'm looking for some advice on the process of reaming this chamber to .308. I have ordered a roughing and finish reamer. Here's my thinking: The "bite" (the radial cut depth) of a reamer, from my experience, for a .447 diameter should be in the neighborhood of .004 to .005". If I attack the current chamber with the finisher it would be cutting about 0.012" from the existing diameter. Therefore I need a rough cut to reduce the bite required by the finisher.

I have chamber reamed several rifles successfully but I always started with a short chamber machined for that purpose. Since I can't use a go gauge during the roughing process how do I know when to stop to leave room for the finisher to do its thing?

This is fun but a little nerve-racking!
 
Interesting. I have a 1916 Spanish Mauser that I had converted over the 7.62x39.
But that was a full barrel kit that Numrich had put out some years ago. Dandy little rifle!
 
Denny Gibson said:
So ... I'm looking for some advice on the process of reaming this chamber to .308. I have ordered a roughing and finish reamer. Here's my thinking: The "bite" (the radial cut depth) of a reamer, from my experience, for a .447 diameter should be in the neighborhood of .004 to .005". If I attack the current chamber with the finisher it would be cutting about 0.012" from the existing diameter. Therefore I need a rough cut to reduce the bite required by the finisher.

I have chamber reamed several rifles successfully but I always started with a short chamber machined for that purpose. Since I can't use a go gauge during the roughing process how do I know when to stop to leave room for the finisher to do its thing?

This is fun but a little nerve-racking!
Click to expand...

Use a reamer stop to control your depth. Most have a calibrated dial so you can adj the depth in 0.001" increments easily.

Make a cut then test with a gauge if you have one. If not you could use a sized piece of brass. Will work for your gun but not someones else's.
 
Denny Gibson said:
So ... I'm looking for some advice on the process of reaming this chamber to .308. I have ordered a roughing and finish reamer. Here's my thinking: The "bite" (the radial cut depth) of a reamer, from my experience, for a .447 diameter should be in the neighborhood of .004 to .005". If I attack the current chamber with the finisher it would be cutting about 0.012" from the existing diameter. Therefore I need a rough cut to reduce the bite required by the finisher.

I have chamber reamed several rifles successfully but I always started with a short chamber machined for that purpose. Since I can't use a go gauge during the roughing process how do I know when to stop to leave room for the finisher to do its thing?

This is fun but a little nerve-racking!
Click to expand...
.001 would be ideal as the finish reamer is bigger in every dimension over the rougher.
 
Denny,

Before you re-chamber the existing barrel with the sleeve. Can you take some pictures. I'm curious to know who made the sleeve or barrel. Rhineland Arms, Troop Systems, etc... or is it a one off creation by a Bubba from years gone by. Moreover I'd like to see the bolt face and the work that went into that because the difference in rim diameter between the 2 cartridges is pretty significant .473" of the 7.62x51mm to the .447" diameter of the 7.62x39mm is a huge difference.

That was a big thing to do back in the day to breath some life back into the small ring family of Mauser's. I have been asked if it is even possible to do what has been done in the past and you have before you an example of that engineering. Of course I said that it could be done but I won't. I thought that you could share that with us before you open it up with a reamer to suite you needs. I'd sure hate to reverse engineer what has been done already.

Jeremy
 
Mauser fan … one thing I’m sure of is there’s no sleeve. It chambers a 7.62x39 round just fine. But the bolt face is for a .308 and the rifling and bore are definitely .308. Will the gun perform well as it is? I’ll leave it alone if I can use .308 bullets and like the performance. What do you think?

I’ll be happy to take some pictures if you’re still curious.
 
That's interesting and I am still very curios. Yes I would like to see some pictures if it isn't too much trouble. If it seems to be in safe shootable shape and you get the performance you are seeking. But this is just me. I'd be inclined to not fix what isn't broken. I have a Spanish lady that I put back together from a pile of parts a couple of years ago that is chambered for 7.62x51mm Nato and I hand load to 300 Savage pressure so I don't have any issues with blowing myself or the gun up. The moral is that it is very easy to tame the cartridge to safe working pressures especially if you use cast bullets.

In all honesty I cant say what I'd do without giving the rifle a thorough check up fist.

Jeremy
 
Scooter22 said:
I have the same rifle and it sounds like someone put a 7,62x39 chamber adapter in it. I had one in mine for awhile. It worked very well. Cartridges would feed if you were careful and eject fine. Prety accurate also. It was loctited in. After about 500 rounds chambering a round started getting tight. I figured the adapter might have been shifting so I removed it. IIRC the adapter was from Ace Dube. It came with it,s own loctite so I,m not sure which. I had to heat the chamber area with a heat gun to soften the locktite and use a stuck case remover to pull it out. It got chipped around the mouth so I never put it back in. If it works ok I,d leave it. Good luck.
Click to expand...
I wasn’t aware of this. Thanks for sharing.

An interesting mystery @Denny Gibson , thanks.
 
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