When those old mausers first came out they were using some pretty heavy 210gr round nosed bullets, and using todays 150-174gr spitzer bullets may affect their stability like some folks discuss in the .223 forums. The original 1898 pattern military ball ammunition was introduced in the Mauser Model 1889 and loaded with a 13.65 grams (210.7 gr) round-nosed bullet fired at a muzzle velocity of 650 m/s (2,133 ft/s) with 2,884 J (2,127 ft⋅lbf) muzzle energy. A certain size bullet shot at a certain speed (fps) needs a certain twist rate to stabilize, ie shoot as accurately as possible. When that doesn't match up, usually your pattern is going to be bigger. Sometimes it means your bullets will tumble (and keyhole the target). I guess what Im getting at is this example. I have an Italian made Replica Remington rolling block rifle chambered in 45-70Govt It was horrible with most Factory ammo Id fed it. Federal 350gr hp, or Remington 405gr jacketed they would all pattern 15" to the left and 22" high of POA at 50 yards. Then I loaded soft lead bullets like 142gr .457" lead ball from my cap n ball revolver, another was a .457" 405gr soft lead gas check HP bullet both loads loaded with Pyrodex R (LRB used a buffer and wad) The Pyrodex loaded rounds impacted exactly to point of aim at the same range! A particular Bullet's size & composition and particular powder/velocity can greatly impact a rifles accuracy. It may take to experimentation to figure what shoots straight out of your particular rifle. Slug your bore, and determine your rifling twist, and work from there. Even in rifle of the same model and caliber there can be a variation in bore diameter. Due to the particular time of mfg, and who made it bore diameter can change. a major difference between Russian and Finnish Mosin barrels is bore size. Measured groove to groove Russian bores have a nominal bore diameter of .311 to .314” whereas Finnish bores had a tighter nominal bore diameter of .3095. The Finnish bore was/is entirely capable of handling any eastern European made .311” factory ammunition though pressures and velocity were/are generally higher than ammunition fired in a Russian bore.