I'd say most smiths know squat about the schmidt-rubin straight-pulls or anything other than the 98 mauser-especially the 1889 model that yours is most likely converted from(because all them old foreign designs are suspect and weak aren't they). The serial number and a search of a Swiss web site such as swissrifles.com would probably confirm the model type. The 7.5X53.5 ammo(not 7.5X55 or GP-11, actually GP-11 is 7.5X55.5)that was designed for use in the 1889 model S-R has an operating pressure range in the 38-40K CUP area, which is right where the 30/30 works at. Does anyone actually know of any mishaps with any Swiss straight-pull?(unlikely) For worry warts a long string can be useful. If it is indeed(probably) in 30/30, then a 30/30 round should chamber properly and go into full battery with no problems and if it is still in the original chambering(7.5X53.5, 7.5X54.5, or 7.5X55.5) then a GP-11 round or anyother 7.5 Swiss round will chamber and go into full battery. Modern(in excess of 40K CUP) ammo is not recommended to be used in the pre1911 type models. If GP-90, GP-90/03, GP-90/23 ammo was not available then and only then as a last ditch effort, GP-11 could be used in defense of the homeland(CH aka Switzerland) when using the any pre 11 type rifle. $100 is a good price especially if you got a magazine with it, as many mags seem to be missing. best-o-luck