Sorry, it's 6.35. I read some blurbs on it through Yahoo search. 1 said it's .25 acp, another said it took obsolete ammo. Which to me meant no longer available. So I'm curious, I also saw 1 in Collectors Firearms. The one I'm looking at is in much better shape cosmectically. I'll know more about it in a week when I actually get it in my hands.