I have a post on here about my wife getting me a new gun for Easter, it is a Ruger Mark 4 22/45 and I love it. A friend of mine when he saw it, had to have one so he went this morning and bought him one from another shop. He paid $500 otd for his gun and its a Mark 4 too just not a 22/45. All I can see is his has a metal frame and mine is synthetic, is that the only difference or what other differences are they. From what I can see, I can't see a $100 difference. Thanks for any help.