Sporterized 1889 Schmidt Rubin. What barrel might I have?

[heofon]

I recently acquired a sporterized Schmidt-Rubin 1889. The receiver, bolt (rear locking lugs), and stock are original, though the stock has been chopped and smoothed to look more like a modern rifle. The barrel has no markings other than Made in Switzerland near the receiver. I would like to know what the chambering is for this barrel and, if possible, where it came from and how old it is.

It has had the rear sight replaced by a Redfield semi-buckhorn sight. The front sight is one of those knurled-base dovetailed blade sights with a horizontal brass insert.

It doesn't exactly look like the Golden State Arms mods.

I imagine I would need to shoot 7.5x53.5 (GP90) or 7.5x54.5 (GP90/23) only, regardless of the barrel caliber, since the old bolts and receivers were not designed to handle the 7.5x55 (GP11) cartridge pressures.

 

[johntheplinker]

Might want to consider having a chamber cast made to insure that it is in fact still a 7.5 chamber. If so, then just stick using the lower pressured ammo and you should be golden.

 

[Hop]

Ammo for the 1889 has always confused me. Most 1889 were converted to fire GP11. My 1889/1911 can shoot GP11 but it's just not very accurate. Would an 1889 that has not been converted still close the bolt on the slightly longer GP11 case? I'm sure my 1889/1911 might do better with the GP90/23 but good luck finding any.

Link for specs: Swiss Handguns 1882