Seems like I have seen posts here from someone with a lathe who does rim work. I have 40 or 50 .44-77 cases made from .348 that need to be thinned to .065 for the C. Sharps style chamber. Thanks if you can help!

Bill,
PM sent.

I usually thin from the rear and deepen the primer pocket if necessary.  It adds an extra step, but is much easier to cut the rim.  Most of the time when only taking a few thousandths off, and the primer pocket is still fine.

If you don't have access to a lathe is there another way of thinning rims? I have to thin the rims on a batch of .35 WCF cases that will not chamber in my Win '95.
Spud

You can always stage the rims down. I once had a hammer swage made for 32-20 to .310 cadet. But a reloading press die would work equally well.

That will work fine. If you can lower and lock your press spindle, you can get it close to the height of a triangular file sitting flat on a steel block. Work slow and it will do a respectable job. The block will give the file much more control.

SBoomer wrote on Jun 10^th, 2024 at 7:23am:

Just to add to this....

Set it up with the case head flat on the block. Then shim the block up the amount you need to remove. Generally 2-3 sheets of paper under will work.

If you use a V block, set it up to support the rim against the pressure of the file. This can produce very good results.

Something else to consider would be if you might use large pistol primers, then take it off the face of the case head to compensate for the difference in cup height.

To further probe the issue of rim thinning, here's another question. Suppose one is working with "modern" .45-70 brass, ie: Starline, W-W, etc., and for one reason or another one had to reduce rim thickness by .015". Would facing off the rear by that amount (essentially removing the headstamp) and then re-cutting the primer pocket to standard depth result in the internal web thickness being reduced unsafely?

Reason I ask is I did that very trick when cobbling together .40-65 cases. I made around 20 of them but stopped before using them when I chose a different solution. (Long story, but that's it in a nutshell.) Have pondered if reducing said web thickness by .015" was risky business or not.

I may be a bit late to this thread but thinning rims is not a hard job and probably best done in a lathe. The best way to thin the rims is from the case side. I have done this back when Uberti first come out with their '76 Winchester. They set the headspace to the original instead of modern brass. The best way I found to thin the rims was to make a plug to fit snugly in the case mouth with a center drill hole in it. Then chuck up a piece of stock and cut a recess to just fit the rim diameter and to a depth slightly less than the rim thickness you need. Hold the case to the recess with  a tail stock center and use a cut off blade or other tool to feed straight in and out to cut the rim to thickness. Takes longer to put a case in and out than to make the cut. It  helps a lot to have the cases sized to the necks are all the same diameter. 
Hope this helps and the pics make it easier to understand. 
Sam

Very nice pics. Yes I have a carrage stop on my lathe that I use. What I do to measure rim thickness is I took a piece of round aluminum longer than the cases, squared eacn end and drilled a hole through that just fits the case. I then use a dial indicator on top of a flat disk on top of the case head to measure the thickness. The disk keeps your indicator tip from dropping into the headstamps.