Well, I’m not proud of this one. I have two M12 Remington slide action rifles, chambered for .22 Remington Special, which as you know is same as .22 Winchester rim fire, .22WRF. I was shooting one this afternoon and had the worst jam I’ve ever had. It was a .22 WMR round, and I had to pry it out of the action with a screwdriver. In two pieces. It being too long, the rear started to come up into the breechblock, but the nose didn’t release from the magazine. Even trying to use the takedown procedure didn’t release it.
Let me say there are several videos on YouTube about the M12, the one most useful to me was about the M12c and the designer, Petersen, noted for the Petersen device also.
A note about these two rifles - I was at the Poulin auction, Fairfield Maine, selling another rifle when the first one came up, so I bid and bought it. It has a date code of 1926 on the barrel, and custom tang sight and front foldable post and hooded bead. I found ammo on the eBay sites, and Winchester and CCI made limited runs of .22WRF. So when I spotted the second rifle on Gunbroker, I bid for it too. It has open sights and a C pistol grip stock. Both have octagon barrels. The date code for the second one is 1931.
So how did I get a .22 WRM round into the .22 WRF box? I do remember being curious as to the difference in case length, and getting a round of each out to measure them - 3/20ths on my scale, .15“ difference. I surmise I put them both back in the WRF box.