Dave, It is a g-series whitetail, in .504 cal, i guess similar to the Bison, In fact I have another one coming from gun-broker, identical to this one with a peep-sight, Just have a hard time passing up a bargain, I slugged the bore on this oneand it might be a hair over .504 so I think I will get some in .5045 and some #2 lube. I tried maxi-balls and they were too small, Great plainsI give a little rap to get them started and they grouped pretty good. Thanx for the advise !!!!!