Mauser Guys - Chamber & Bore Dimensions?

[DocRock]

New rifle, won at auction:

Early Gewehr 98 receiver (between 1898 and 1903, based on proof marks), later barrel - octagon to round - age unknown, much engraving, case colored action, nice claw mount bases, double set trigger, fine stock, etc.

Have slugged the bore and done a chamber cast. Getting the following dimensions:

.3135-.314" lands .323-.3235" grooves.
Short leade at .3265" and a tight chamber of .356-.3565" at the case mouth.

Edit: Had a brainwave and tried a factory S&B 196 grs SPCE. It chambered. Tight, but chambered. My 8x57js reloads are neck sized only and the bolt does not want to close on those.

So, what's going on? My take is: jolly nice custom gun with a tight chamber intended for the post 1905 7.92x57JS. I am out of my depth here, but it seems like a German inter-war version of a match rifle chamber. But, it's awfully tight. Any experience of this? Advice and counsel? Direction to further resources/gurus?


Thanks very much.

 

[GooseGestapo]

Slug the bore!
Many commercial pre WWI rifles were chambered for the 7.92x57 J, or 8mmJ.
This spec has a .318” groove and .312” bore.

It was preferred for hunting applications due to heavier bullet, round nose ammo. The later 8mmJS was the military spec with spitzer ammo.

DO NOT shoot .323” 8mm ammo through it till after you slug the bore and confirm a .323” bore.

 

[792mauser]

If the grooves are .323+ then it looks like a tight chamber.
Fully full length size a dummy ctg and trim then see where that leaves you

 

[DocRock]

Slug the bore!
Many commercial pre WWI rifles were chambered for the 7.92x57 J, or 8mmJ.
This spec has a .318” groove and .312” bore.

It was preferred for hunting applications due to heavier bullet, round nose ammo. The later 8mmJS was the military spec with spitzer ammo.

DO NOT shoot .323” 8mm ammo through it till after you slug the bore and confirm a .323” bore.

I gave the dimensions after slugging the bore and doing a chamber cast...

 

[GooseGestapo]

Sorry, somehow I overlooked the dimensions.
Most of the custom shops used their own proprietary reamers.
I’d bet it shoots real good.

 

[Dave DeLaurant]

If the grooves are .323+ then it looks like a tight chamber.
Fully full length size a dummy ctg and trim then see where that leaves you

Good advice, to which I would also add the following:

Bob Bell wrote up a personal horror story about a custom re-case hardened Mauser 98 receiver that blew up and nearly blinded him



From his description, the action on his rifle was custom reworked between the world wars in the similar manner to yours. I won't speak for anyone else, but his tale gives me the willies!

Lacking a definitive non-destructive way to confirm the soundness of a re-heat treated action such as this, were this my rifle I would be inclined to limit shooting to cast bullet handloads.

 

[Nature Boy]

Good advice, to which I would also add the following:

Bob Bell wrote up a personal horror story about a custom re-case hardened Mauser 98 receiver that blew up and nearly blinded him

View attachment 916576 View attachment 916577

From his description, the action on his rifle was custom reworked between the world wars in the similar manner to yours. I won't speak for anyone else, but his tale gives me the willies!

Lacking a definitive non-destructive way to confirm the soundness of a re-heat treated action such as this, were this my rifle I would be inclined to limit shooting to cast bullet handloads.

That is scary

 

[DocRock]

Good advice, to which I would also add the following:

Bob Bell wrote up a personal horror story about a custom re-case hardened Mauser 98 receiver that blew up and nearly blinded him

View attachment 916576 View attachment 916577

From his description, the action on his rifle was custom reworked between the world wars in the similar manner to yours. I won't speak for anyone else, but his tale gives me the willies!

Lacking a definitive non-destructive way to confirm the soundness of a re-heat treated action such as this, were this my rifle I would be inclined to limit shooting to cast bullet handloads.

Thanks for sharing. That is scary. I take some comfort from the fact that my receiver is a Gewehr 98 receiver stamped with the proof load (for the Mk88 Patrone, 1893-1901) so will stick to sub 40,000 psi loads.

 

[Mr. Zorg]

Good advice, to which I would also add the following:

Bob Bell wrote up a personal horror story about a custom re-case hardened Mauser 98 receiver that blew up and nearly blinded him

View attachment 916576 View attachment 916577

From his description, the action on his rifle was custom reworked between the world wars in the similar manner to yours. I won't speak for anyone else, but his tale gives me the willies!

Lacking a definitive non-destructive way to confirm the soundness of a re-heat treated action such as this, were this my rifle I would be inclined to limit shooting to cast bullet handloads.

Another thanks for posting this.