1892 Winchester Conversion

[SRE]

It's looking like I'll be taking on a bigger project here in the shop. A Winchester 1892 25-20 that has been attempted to be converted to 357 mag. Apparently the only thing done to it so far has been the barrel/ chamber work.

Anyone have any experience with this procedure? There is a good bit to it. Fortunately the rifle will be my own so I can really get into it without the stress of knowing it belongs to a customer.

[Clark]

My brother bought the 256 Win reamer thinking he would do the same.

I just googled it, and I have to read 20 posters saying "don't do it" before I ran into one who explained the process:

Couple of things that I ran into while doing the conversion from 32-20 to 38 spc/357.

The biggest challenge is the rim diameter: 32-20 is .408, .357 is .440.

This requires that you first open up the magazine tube hole in the frame to accommodate the larger rim dia. I did this in the mill, with the frame mounted on an angle plate.

Couple of things to think about:

Winchester originally machined the hole at .430, giving the ctg head .023 of wiggle room for easy feeding. It would not be a good idea to allow that much “wiggle room” in the conversion, as the ID of Winchester mag tubes can vary; I’ve measured a range from .456 to .470, then you need to consider dents, ding rust etc on the inside of the mag tube.

So if you machined the frame to allow .023 wiggle room (.473), then the lip on the follower will most likely exceed the ID of the mag tube.

Since I make my own mag tubes, I used cold drawn tubing with a consistent .465 ID. I machined the hole in the frame to .450 (.010 wiggle room) and machined a new follower with a lip dia of .460.

The frame is soft so HSS will work fine.

The L & R ctg guides will need to be thinned to accommodate the larger rim and the larger OD case body. It’s best to remove the material from the backside; I put them on the surface grinder, think I took off about .018 from either side.

The bolt face and ejector will need to be opened up to accommodate the larger rim, the bolt is easy to do in the mill with standard HSS cutters, the ejector is made out of hardened steel so you will need to use carbide on that.

The rim recess on the original (32-20) 1892 bolts, were set up with for a.065 rim thickness, the standard rim thickness for the 38/357 is .060 so using the original barrel you already have .005 excess headspace. I solved that by using a new barrel and making the shank longer and facing off the bolt to get the .060 deep rim recess.

The extractor will need to be modified; it will hit the frame when it tries to go over the larger rim.

The carrier will need to be modified to provide a better angle on the straight wall case, but hats a cut and try effort.

It’s been a while since I did the conversion so I may have missed a couple of things.