A fellow on another site has a 1891 Belgium Mauser rifle that he has slugged and swears the bore is .320 and not .311/2. He has tried to fire 7.65x53mm ammo and the bullet will not stabilize. The fired cases have a larger than normal neck after firing. The bore is like new, the crown has no damage.
During the post another member says he has ammo from around that time that is 7.92x53mm. Was there such a cartridge issued to the military? For sporting use? Is there any history than can be read on line on this cartridge?
Thank you for your time.

Bore or Groove diameters?

The original 7,65 Belgian Mauser had a BORE of .301-.302", and a GROOVE diameter of .312-313"

The “7,92” (ie German) had a BORE diameter of .311", and a GROOVE diameter of .320 (“J”) or .323" (“JS”).

NO military cartridge “7,92x53” BUT there is a 8x54 Swedish sporter ( “8mm” on a 6,5x55 Case) and also a 8x54 Mauser “K” Sporting cartridge
(uses the “J” bullet, .318-9" diameter, .320 groove…using a shortened 57mm case.

Next Possibility: “Civilianization” of a Military calibre rifle by “freshening out” the rifling to use a larger diameter bullet ( France did something similar to this to Military chambers for years to prevent use of “Military” ammunition in Milsurp rifles, only Handloads or special custom commercial ammo.)

The only manner to find the correct calibre and chambering is to Chamber cast and also to slug the barrel, and use accurate measuring tools to get the measurements.

Doc AV

Thank you for the reply Doc. I passed the info to the owner of the rifle.