doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Resizing RMC hulls

I've got maybe a dozen or so 10 gauge RMC hulls that I bought used and won't chamber in my Spanish double.

Is there any relatively easy way to resize them that doesn't include the use of expensive tools like lathes or other such machinery?

Worse comes to worse I could always make a couple of sets of wind chimes with them.

A sizing die, CH4D makes them.

Has anyone actually re-sized a RMC hull with a CH4D die?


I am reluctant to spend the money they want for the die. It would be cheaper to buy more hulls and I've never had to re-size one of the new hulls I bought from RMC.

I have used the 12 ga version to resize a few RMC brass hulls after shooting them in a gun with larger chambers. You need to do it gradually, just a bit at a time, or they get stuck.

Based on my experience reloading and reforming brass rifle cases it agree with LGF. Go incrementally with a good case lube. Not Hornady One Shot. I’d try Imperial Sizing die wax and size 10-15 % then back out and re lube. Not enough wax to cause dents just a thin film to allow the next increment. Apply wax with your fingers to insure a thin, uniform coating. As you do it you will develop a feel for how much to size and how much to lube.

I think it would be better to start with smoking several of the RMC shell cases and seeing just where the interference with the chamber is. Then compare measurements of the cases to SAAMI standards. RMC makes lathe turned cases with thicker walls than some other brands, and also custom makes cases for oversized chambers. Sizing the forward part where the case is thinner will naturally be much easier than attempting to reduce the size close to the rim.

It would also be a good idea to measure the chambers of your Spanish double to see if they are the real problem. If the chambers were reamed undersize, it might be cheaper and better to have a gunsmith run a correct size chamber reamer in them that might then permit chambering of the RMC brass cases.

No way I would buy the CH4D sizing die to just resize a dozen RMC cases. Plus you also need a press with the 1 1/4"-12 thread size for the die. It would be cheaper to buy new RMC cases made to fit your chambers.

I know someone who has a CH4D 10ga sizing die and he just ran through some RMC cases for a friend, it worked fine. We shoot big bore rifle so big dies are not a problem, my Hollywood press takes 7/8" and 1&1/4". The real problem with having RMC turn brass to fit your chambers is that they are 2 years out on orders. That is actually how we ended up with the RMC brass that needed to be sized, it was bought at auction to avoid the wait, in our situation sizing the brass was the right answer.

In answer to your question, NO, there os not an easy way.

I agree with Keith’s view.

Evaluate the actual difference in the hull from the chamber to see what the best course maybe.

I gave up on resizing RMC cases. I keep them separated into tight chamber and loose chamber lots and keep them segregated.

I've never done as large a brass case, but I have cobble up rounded, way larger diameter than the case, clamping surface jaws for a vise to reduce the base of some brass. Put a bit of a polished finish on the faces that touch the brass. Then, just do a bunch of light bumps and turns, slow going but doable for a small batch. I'd use a regular sharpie to make a couple or a few opposing lines on the case, should be able to see where it hangs up in the chamber. Anneal, if needed. Just a thought, good luck with it.

I don't think the chambers are overly undersized, because I only have issues with less than a dozen of the cases. The old antique hulls and plastic hulls are also fine. I even gave the ones that didn't fit to a friend who also has a 10 gauge, and they didn't fit in his gun.

I think I have between 75 - 80 brass 10 gauge hulls between RMC and the antique ones. Maybe the oversized ones will end up as wind chimes after all.

Thank you everyone who replied.