Just be careful. Drag out your screw-pitch gauges and see what you REALLY have.

LOTS of Mausers were made on BRITISH machines using "Imperial" (and VERY Britishicon threads). This was because Britain was the leader in metrology and machine design in the late 1800's. LOTS of on-line thread data available.

The REALLY curly ones are actually the British small arms like the Martini and Lee-Enfield series, (BEFORE the No4). Most of the "small" threads are made to "Enfield" standards of diameter AND pitch AND thread-form, which significantly pre-date the adoption od BA, Whitworth, BSF etc.

Mauser breech threads are Imperial and WHITWORTH (55 degree) form.

Mosin Nagants have IMPERIAL breech threads, ditto the Arisakaicon 30 and 38 series. The Type 99 is seriously Metric, however.

Many also have Imperial front and rear trigger-guard screw threads. Not surprisingly, this made it easier for folks in certain "Imperial" measurement countries to "Sporterize" millions of them.