Converting an Old Rusty 32 Rimfire to 357 Magnum

   08.08.19

Converting an Old Rusty 32 Rimfire to 357 Magnum

A while back, we shared a video of Larry Potterfield converting an old Remington rolling block rifle from 32 rimfire to 32-20 centerfire. This time, he’s going to do a similar job on a Winchester 1885 low wall single-shot rifle.

The rifle he’s working on was originally 32 rimfire, but the bore was damaged with rust pits. So he had it bored out, rifled, and chambered for 357 S&W Magnum.

After removing the old rimfire firing pin, which was off-center to strike the cartridge rim, he drills and taps the firing pin hole and fills it with a screw generously coated with green Loctite thread locker. He also peens it in place. Once that hole is filled, he uses a bushing to guide his drill bit as he drills a new firing pin hole through the breech block.

He has a centerfire firing pin for this model rifle, but its tip is broken off. So he fixes it up by facing it in a lathe and installing a hunk of drill rod, then shaping the rod into a proper firing pin that will safely and reliably detonate centerfire primers.

He uses a centerfire breech block as a guide to tell him where to drill a vent hole in his converted breech block, to help vent gas away from the shooter’s face in the event of a pierced or ruptured primer.

From there, he needs to modify the extractor to make it work with the larger 357 mag cartridge.

He heads to the “range” with his once-again-useful old rifle. Unfortunately, he doesn’t have a good backstop behind his target, and he didn’t proof-test the gun (at least not on camera). This are serious oversights. But his test shows that his firing pin is in the wrong place! So he goes back to work.

He decides to create a new breech block link, which will place the block slightly higher in the receiver to properly align the firing pin with the cartridge. So he makes one of brass as a test fit… and then he makes a couple more, until he gets it right. Then he makes a steel link, case-hardens it, and shoves everything back together.

Back at the “range” again, it goes bang just as intended. Nice!

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