If you are new to Mauser - Land, a quick way to tell if the action is a 98 style (strong) action, is to see if it cocks when you open the bolt. The 91s, 93s, 95s and Swede 96s all cock the firing pin when you close the action.
I have seen many, many, many older Mausers that were mislabeled by gunstore employees...as 98 type actions...do not go by the tags alone...
Here is a little info on the action sizes...
1) Small Ring M-1893-1896
1.30 in dia.and are 8.50 in length, Straight walled receiver with screw spacing of 7.620.
Small ring have a threaded shank diameter of .980 in. With 12 threads per inch.
These include M-93-96 by Spain, Sweden, Germany. Spanish M-93 bolts have flat bottom, DWM M-95 bolt faces are round. Swedish bolts M-38/94/96 will fit only Swedish.
2) M1910, M1936 Mexicans by FN and Mexico,
1.30 dia. receiver ring,
8.50 in length, with screw spacing of 7.620. Barrel Shank .980
Small ring have a threaded shank diameter of .980 in. With 12 threads per inch
The barrel is a 4-groove with a twist rate of 1:9
Receiver is slightly different from other Small Ring. Mauser (Bolts will not interchange with any other type Mauser).
3) WWI German KAR98A,
1.30 dia. receiver ring, 8.750 in length, with screw spacing, of 7.835 (Long action, Small ring).
Has a threaded shank diameter of 1.100 in. With 12 threads per inch. WWI carbine, Uses a standard M-98 Bolt.
4) Intermediate Large Ring M-98 ,(Large ring, Short action) M-24
1.410 dia. receiver ring, 8.50 in length, with screw spacing of 7.620
Intermediate Large ring have a threaded shank diameter of 1.10 in. With 12 threads per inch.
Mexicans by FN and Belgium, the M24, M47, M48 by FN and Yugoslavia. A large number of M48 Yugoslavian large-ring M98 Mauser have recently been dropped on the market. This M-98 short is considered an intermediate action, and WILL NOT fit a Standard 98 Mauser stocks and standard bolts will not interchange..
5) Large Ring M-98
1.410 dia receiver ring, 8.750 in length, with screw spacing of 7.835. Barrel Shank of 1.100
Large ring have a threaded shank diameter of 1.10 in. With 12 threads per inch.
Including M-98's from WWI and WW2, GEW-98,M-98k, CZ-24, VZ-24,Spanish M-43/44 . Chilean M1912, Steyr Brazilian M1908/34, Brno 98/22, 98/29, DWM / Argentine. M1909, M24/30 Venezuelan, FN M1935 Peruvian, FN Standard Model, Mauser Oberndorf
6) M-33-40 Small Ring,
Long action. Lighting cuts on sides of receiver.
1.30 dia. receiver ring, 8.50 in length with screw spacing of 7.835.
Large ring have a threaded shank diameter of 1.10 in. With 12 threads per inch. Brno Vz-33, CZ-33/40