I acquired a rifle a while back that was presented as a 375 H& H. It is a Winchester action but there is no stamp on the barrel (or anywhere) that would indicate the caliber. It may be an aftermarket barrel I assume? My question is how can I determine if it truly is a 375 H&H? I am a little reluctant to just throw some 375 H&H ammo in it and shoot. Thanks for the advice from those who know more than I do.