When I was a young (and I am sure some of you remember this) they used to have magazines that came around and in the back were pages of Army Surplus rifles you could purchase for just a couple dollars. I mean like for $20.00 you could get a rifle. Why I never went for that I have no idea. Maybe I did not trust the add in the magazine, as it sounded too good to be true.
A friend of mine had a rifle that looked identical to that. All he ever called it was his Russian Gun. And it was a 7.62x54 (I believe it was). It was really accurate, and sure laid out deer nice. He used to order cartridges from Sportsman's Guide I believe it was. But he sold it because the shells were hard to find around here, and expensive. He ended up getting a simple old 30-30 Winchester.
That is a nice looking rifle. I hope the wife catches you and slaps the snot out of you... Just kidding. Hide it and then deny anything you are accused of.