Identifying this Mauser and the cartridge it takes

[Huvius]

It’s the “unknown 9x57”

Well it definitely has a “rim” recess but a Mauser would have that type of recess only on a belted cartridge.
On a Mauser or any bolt action for that matter, the rim of a cartridge, whether rimless or rimmed, is contained within the face of the bolt itself behind the extractor claw.
The chamber cast won’t show whether its rimmed or rimless.
I don’t know if I would feel all that comfortable shooting a standard 9X57 in that chamber.
Looks like a prime area for a head separation.

 

[SkullKeeper]

Well it definitely has a “rim” recess but a Mauser would have that type of recess only on a belted cartridge.
On a Mauser or any bolt action for that matter, the rim of a cartridge, whether rimless or rimmed, is contained within the face of the bolt itself behind the extractor claw.
The chamber cast won’t show whether its rimmed or rimless.
I don’t know if I would feel all that comfortable shooting a standard 9X57 in that chamber.
Looks like a prime area for a head separation.

Yes sir, I’m going to rebarrel this rifle anyhow. I think it will be a great 318WR.

 

[Boone66]

It is stamped as 7.9
In my opinion this is: 7.92×57mm Mauser. (also known as 8mm Mauser, or 8x57)
Commercial designation 8x57 JS
Bullet diameter .324

My 9x56ms is also stamped 7.9, sometimes that's the bore size, not the groove diameter. A chamber cast and bore slug will tell you the actual size.

 

[Boone66]

Probably 9x57. Had a similar issue. Was able to chamber 8x57 brass but not 9.3x57. I slugged the barrel using soft lead fishing weight. Measured .356= 9mm.

Those 9mm barrels will be between .356 and .360, is my experience. .358 cup and core bullets can be resized to .358, with a sizing die, custom bullets can be made also. Some folks say .366 bullets can be reduced to ..360, but I haven't done that yet.

 

[SkullKeeper]

My 9x56ms is also stamped 7.9, sometimes that's the bore size, not the groove diameter. A chamber cast and bore slug will tell you the actual size.

This was the cast , do you have dimensions of a 9x56ms ?

 

[Boone66]

This makes me wonder how the smith plugged the chamber for the casting. The “rim” might just be what settled against the plug that wasn’t fully seated.

The plug goes in the bore, then pored from the breach end

 

[Boone66]

This was the cast , do you have dimensions of a 9x56ms ?

I'll measure one of.mine when I get.out to the shop. They are.very similar cartridges, but the MS is a lower pressure.

 

[Milan]

Sorry for the confusion but which chamber is the photo above with the recess circled in red?
If it’s indeed recessed, that would be for a belted cartridge.

I think that might be the c-ring in the Mauser front action ring. All Mausers hedspace against it. That’s how they were able to just screw barrels on (original “pre-fit barrels” before they were called that ). Only the rimless rim/extractor groove part would be unsupported by the chamber but surrounded by the bolt part around the face. I too was inclined to think it was regular 9x57 rimless. But hey, I’m no expert. Just an enthusiast.