Boy, did you ask the wrong question!
Approx. .50 caliber (no chance I'm measuring the bore on this baby)
hammerless mechanism, hair trigger
loaded with whatever ol' Whitey had for dinner last night.
Believe me, you don't want to get hit with this thing...
I would post a pic of a real gun but they are all under lock and key, with a 5 year old in the house I figure I probably have more to fear from my own guns than someone else's. Once my son is old enough to understand gun safety I will put Whitey back in her holster...
Both are great guns, but I actually prefer the 75B because of the cost of ammo and the quick return to target that the lighter round allows. Having double the ammo doesn't hurt, either.