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

That additional information helps tremendously. Chamber dimension specifications do have tolerances, but it sounds like yours are probably in spec. It makes me wonder if the problem cases were made at the same time as other RMC cases you have, and whether they simply became expanded after being fired in another gun that has larger chambers. Brass has been used for cartridge cases because of the special properties it has compared to many other metals. It is ductile and relatively easily machined or formed. When fired in a gun, the cases expand to fill and seal the chamber to prevent gas leakage, but almost immediately upon firing, they then contract a bit which permits easy extraction. But after fire forming to one chamber, they may not fit another very slightly smaller chamber unless they are resized.

I don't blame you for not wishing to spend a relatively large sum for a 10 ga. sizing die and suitable reloading press. It just doesn't make economic sense for less than a dozen cases. 10 gauge brass wind chimes sound interesting, but I'd still want to explore other options. I'd still want to smoke some of the cases, or mark them with a machinist layout blue like Dykem to see just where they are hanging up. Measuring the cases and your chambers would tell you how much sizing is needed, or alternately, how much metal might need removed. As noted earlier, RMC brass is lathe turned, and is thicker and heavier than other brands. It might be possible to have a machinist take a very light cut with the cases on a mandrel between centers to make them useable. Someone who owns a lathe might be interested in buying them and either doing that for himself, or even machining a simple sizing die that could be used in an arbor press.

Maybe you could find someone who has a sizing die who could size your cases. It would be nice if there was some source to just rent a sizing die, in the manner that gunsmiths often rent chambering reamers. Just a few options that you might consider, and others may have better ideas now that we know the problem is only confined to less than a dozen cases, and you have others to use.

I agree with keith - do the measurements - chamber, the oversize cases then the ones that fit. Compare the non-fit vs those that fit and that would help to undertake reducing the outer wall of the oversize cases in the appropriate place(s). Probably straightforwaed work on a lathe?

Someone was gracious enough to make me one for free using a block of steel about 10 years ago based on a post about this subject I had made on a different forum. Even with sizing wax and a 1 ton arbor press there were cases that would not go all the way into the die. Based some of the posts above I may try again with the more gradual approach. I had bought a bunch of used RMC 10 g hulls at a very fair price. I believe the seller had gotten some of those used as well and whatever shotgun they were used in must of had oversized chambers.

I think this question pops into my mind every 5 years or so and I think I got a lot of information I can use from this thread that I don't remember seeing before.

I've done this in the shop one other projects to fit tubing.

Take a heavy block of steel long enough to roll a 10ga hull across and place a bar of steel wide enough to cover the whole case or enough to cover the amount you want to size. Leave the rim hang over the edge and roll the case back and forth between the bar and block increasing pressure until you sized it enough, apply pressure in small increments so you don't make it oblong.