It’s .22 Strangest 22 I’ve seen for awhile. It’s a falling or rolling block Breech. Tilts down and hold every thing put.
I don't have my M51 in front of me but I don't think it does have a hold open. If it does you would pull the bolt back and push the cocking handle in.
Thanks. What type of Ammo is needed to cycle the Mossberg? It’s just a hair younger than me and I’m pretty weak these days. I’ll start on the soft side til I get it to cycle. The Brno looks new so I would think it can take most Ammo but again I’ll see what it likes and start at standard velocities.
Cheers