Identifying this Mauser and the cartridge it takes

[eshift]

S&S stamp ( Sauer and Sohn)

 

[MontanaGrant]

Chamber cast sounds true.

This is a stupid question but I have to ask: Is it rifled all the way to the end?

I’ve seen a number of rifles that have been counterbored, possibly due to muzzle damage. Then the bore is larger than the rifling back for an inch or so.

 

[Ericedwinbates]

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.

 

[SkullKeeper]

Chamber cast sounds true.

This is a stupid question but I have to ask: Is it rifled all the way to the end?

I’ve seen a number of rifles that have been counterbored, possibly due to muzzle damage. Then the bore is larger than the rifling back for an inch or so.

Yes sir, it’s rifled to the end. I didn’t realize they did what you described - interesting fact.

 

[cmk]

It is very difficult to judge a rifle based only on photos. The proof-marks seem to be German. N under a crown means that the rifle is Nitro proofed. 7,9 mm is the designation for a barrel caliber 8mm/323. However, the stated relatively weak proof-load of 2,75g powder suggests a weaker cartridge than the 8x57IS. The magazine length fits a cartridge with a 57mm case. Since the diameter of the barrel is rather .358 than .323 and taking into account the reduced proof-load, it is quite possible that it was a rifle initially caliber 8x57IS rebored to caliber 9x57.

My guess is that this rifle started life as an 8x57I, rather than the 8x57IS. That is the old pre-WWI Patrone 88 with a .318 bore rather than the modern .323. It worked at a lower pressure, and was proofed with a 2.75g load of smokeless powder (according to wikipedia at least).

Patrone 88 - Wikipedia

en.wikipedia.org

That would also explain why somebody went through the trouble of re-boring it. .318 bullets and ammunition are a lot harder to find, and the 8x57I caliber is rather obsolete.

What it is now is anybody's guess until you get a chamber cast.

 

[grand veneur]

It could be that it was initially a rifle caliber 8x57I and then this would explain the reduced proof-load, but I assumed that the rifle was tested again after the reboring. As already written, without holding the rifle in the hands and being able to inspect it, it is difficult to have an opinion.

As the cartridge 9x57 is concerned, she is also nowadays not much more available than the cartridge 8x57I. Usually, damaged or worn barrels are rebored to a bigger caliber, which in the case of a 8x57 cartridge is the 9x57 cartridge.

 

[Milan]

7.9 is the same bore dia for both .318 and .323 groove barrels. Based on the 2.75 proof mark could be .318. But N proof means Nitro proofing which I think was for the .323 barrels. So, none the wiser. Either way most likely 8x57I or IS rebored. To what? Casting it will tell. I thought the OP was going to do that. Any results yet?

 

[SkullKeeper]

7.9 is the same bore dia for both .318 and .323 groove barrels. Based on the 2.75 proof mark could be .318. But N proof means Nitro proofing which I think was for the .323 barrels. So, none the wiser. Either way most likely 8x57I or IS rebored. To what? Casting it will tell. I thought the OP was going to do that. Any results yet?

I dropped it off to have it done but not heard back yet on the results. I’ll let everyone know when I find out .

 

[SkullKeeper]

The long awaited chamber cast is complete and results are ….

9 x 57 R

 

[Velo Dog]

Hello Skullkeeper,

If the “R” designates “Rimmed” (the chamber cast appears to be exactly that), is the magazine a “Slant Box” ?

If it is, and even if ammunition is available (I bet it is scarce), I would not bother firing it.
Instead, the very first thing I would do is have it re-barreled to .303 British caliber and reinstall the original sights or a reasonable set of vintage style express sights (Recknagel of Germany comes to mind).

That said it is not mine to decide.
But if it indeed is a slant box Mauser, oh how I do wish it were mine.

Best Regards,
Velo Dog.

 

[sgt_zim]

I was thinking that 9mm is .360” … but as you say there probably is a variance

True 9mm is .355

 

[Huvius]

Well that’s interesting.
The action doesn’t look like it’s a slant box so the cartridges will need to be loaded with the rims one in front of the other.
I’ve seen a W.W. Greener 303 on a standard action so that’s not unheard of.

The bolt face and extractor are opened up to take the rimmed cartridge?
If an 8x57 cycles and ejects, it may not be which would be weird.
That would have been a good thing to look at right off the bat.