Groundhogs are fun. About that same age I had a Ruger 223 modeled like an M-16 with, get this, a 10x scope! The GH's never stood a chance. We got $3 a pelt. Not sure what happened to that rifle. I think my Dad lent it out to one of his friends, or traded it. By the time I noticed it was gone, I was already in college and $3 a pelt just wasn't appealing. There were other pelts that suddendly caught my attention.
I had a Winchester 255 (I think it was) lever action, with a 3-6 scope. Not a cowboy type rifle, a bit more modern. Sold it (foolishly) when I was in college, as I didn’t use it much by then. But the folks who bought it no doubt taught their two boys to shoot, so all is good.
One time, I almost shot a mouse at about 75 yards. Was shooting at a patch of dirt on a hill across a field. There was a dark spot I aimed at. Turned out to be a mouse hole! Shot a couple times, dirt would fly then a puff of dust. WTF? Third time I shot, I saw a mouse take off. He was trying to kick out the dirt I stirred up. True story.
My brother decimated the ground hogs and I never did get one.