Author Topic: How I convert centerfire brass to rimfire  (Read 384 times)

Offline ndnchf

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How I convert centerfire brass to rimfire
« on: April 24, 2021, 08:26:25 AM »
There has been a lot of interest in the rimfire cases that I make from centerfire brass. Since I'm in the process of making 10 more .44 long rimfire, I made a two part video on the process I've come up with. Maybe this will inspire you to makes some of your own :-)



"We're all travelers in this world.  From the sweet grass to the packing house, birth till death, we travel between the eternities"  Prentiss Ritter, Broken Trail

Offline ndnchf

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Re: How I convert centerfire brass to rimfire
« Reply #1 on: April 28, 2021, 12:12:11 PM »
A follow up to the process of converting centerfire cases to rimfire. When making the new offset rimfire primer pocket, the hole is finished with a .224" diameter reamer. This gives the .225"- .226" diameter acorn blanks a press fit. This is good to minimize gas leakage when firing. Sometimes the acorns can be thumb pressed into place, other times it takes a bit more pressure to seat them.

After chewing on it a while, I came up with a way to seat the acorns in the loading press. First I rummaged through my dies to find one that the .44 long rimfire case would slip easily into, yet the rim would seat against the bottom. It turns our that a .45acp sizing die was perfect.

Next a flat topped ram was needed to press the acorn into the pocket, flush with the back of the case. Basically a replacement shellholder, but with a smooth flat top. The critical measurements were taken off an RCBS shellholder. Then over to the lathe to turn it out.

I just primed 20 cases and it worked great.
"We're all travelers in this world.  From the sweet grass to the packing house, birth till death, we travel between the eternities"  Prentiss Ritter, Broken Trail

Offline ndnchf

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Re: How I convert centerfire brass to rimfire
« Reply #2 on: May 13, 2021, 05:18:59 PM »
I made a couple more tools to make reloading these rimfires a little easier. First is a decapping stand and custom punch to knock out the fired acorn blank primers.
"We're all travelers in this world.  From the sweet grass to the packing house, birth till death, we travel between the eternities"  Prentiss Ritter, Broken Trail

Offline ndnchf

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Re: How I convert centerfire brass to rimfire
« Reply #3 on: May 13, 2021, 05:22:03 PM »
I've made a few reloadable .56-50 rimfire cases as well as a bunch of 44 long rimfires. The most tedious part of the process is measuring and marking exactly where to drill the pilot hole for the new offset chamber.  I'm using a caliper and magnifier on my glasses to see and mark each one. Inevitably there is still some variation.  I want to make more .56-50,  so this past week I've been trying to think of a better way. Here is what I came up with.

I made a jig that has nub precisely machined to fit in the centerfire primer pocket. The jig OD is the exact same diameter as the case rim - .650". Using the edge, I measured in and marked the spot on the jig where I want the pilot hole. Then a 3/32" hole was carefully drilled through the jig. To use it, the jig's nub is placed in the centerfire primer pocket, then a 3/32" transfer punch is placed in the hole and tapped with a hammer. This puts a dimple at the same spot on every case where the pilot hole needs to be drilled. I made one .56-50 tonight with it and it worked well.  But rather than cut up my precious stash of .50-70 to make more, I just ordered 50 Starline .56-50 cases from TOTW. 

I think this will make the process go easier.
"We're all travelers in this world.  From the sweet grass to the packing house, birth till death, we travel between the eternities"  Prentiss Ritter, Broken Trail

 

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