I made a die to size case bases.
300 RUM brass is hard to find and very expensive when you do find some. I bought some once-fired brass off Gunbroker.com last month and they wouldn't chamber in my .338 Edge. By all appearances the brass was as advertised by the seller. I tried to size them in my dies but they wouldn't size the base down to under .549. If I screwed my dies down until they touched the shell holder my headspace was WAY too much. If my bases are over .549 they chamber hard and a couple that were over .550 stuck in my chamber. Apparently the gun these cases were shot in has an oversized chamber(?). So now I'm into 100 brass for $150 and I can't shoot them.
Larry Willis makes a collet-style base resizing die for 300H&H based belted cases. For $98, if it works, it should pay for itself the first time I use it. I contacted him and he said his dies wouldn't work on 300RUM cases. Dang! After many emails we came up with a plan. I would make a pass-through style die that I could force a case up through the bottom and out of the top. Larry's only caution was to watch out for "plowing". I guess when you resize bases, the bottom of the die will sometimes push brass down to the base and leave a thick area just ahead of the belt. Even though mine aren't belted, he wondered if that might happen and I would end up with a seized case.
I vaguely remember, many years ago, taking some rifle brass with loose primer pockets to a friend and having him run them up and out through a pistol die. This "squeezed" the casehead and primer pocket back to where the primer fit like it was new brass. Sooooo, I thought i'd try to make my own. I took a 1" stainless bolt, and a lot of time, and made a pass-through die.
I used a 300WSM chamber reamer to get a tapered bore. It was tricky getting the exit exactly .548. I alternated running a telescoping bore gauge and lightly reaming until I finally got it.
I know the bore inside the top of the die looks pretty rough but there's a shoulder about halfway down that's polished with 500grit, 1000grit, steel wool and lapping compound on a cloth. It came out mirror smooth. It's not carbide but I'm hoping stainless will hold up if I use a liberal smathering of Imperial Sizing Wax.
Well, by dang, it worked!! All my cases came out at .547 - .548". All of them chambered nicely too.