I believe that it was a made up rifle. Packs a wallop! The bolt is flat where it enters the breech. On back on the bolt is a small metal rod the catches on the release and cocks it.

You can also cock the bolt release by hand if you push that little medal rod to the side.

Lots of welding on the tubes but they look like a good job. I will try yo take some images of the breech etc.. Stock wood looks like walnut
I keep warning my friends that i am going to find the proper equipment for it and take it deer hunting! LOL.