A lot of people will have a kitten if you want to slug a cylinder before you buy a gun but if you have a pin gage, they're cool with that. You can buy them from Meyer gage co in individual pieces without having to buy the entire set and they are very reasonable. The ones I bought for 45's are .450 through .458 in 1 thousandths increments and IIRC, they were about $3.50 each. Us wheel gun junkies should have them and eliminate the guessing. As far as relying on the size of a bullet printed on the box...well it is a lot closer than a shot in the dark. It's not a 625 but my 25-5 from 1988 has .451 cylinder throats and a .451 barrel. I believe that mama had fixed the throat problem by then but with the pins, you will know for sure. Keep us posted. Murf