My dwindling supply of .25-20 brass has finally reached the critical point, ie. less than 50 cases remaining. After re-reading the posts here and elsewhere on case forming, I found a successful set of procedures that work for me and my 1935 vintage Winchester Model 65 lever gun.
I used new Starline .32-20 brass for my case conversion, but did briefly try a couple from of my hoarded supply of .218 Bee. The "Bee" brass was Starline as well and new; and was easy to expand out to .25-20 after lubing the inside neck with Imperial Sizing Wax. I used my RCBS FL sizing die and removed the decapping rod for the operation, then neck expanded the case using a Lyman .258" dia. "M" die. While this worked easily enough, .218 Bee brass is as scarse as .25-20 so it was no help.
Turning to the new Starlijne .32-20 brass, I began by annealing ten pieces using the torch method for a brief 5-6 second flame immersion, then applied a light coating of Imperial Sizing Wax, both inside the neck and outside down and just barely over the shoulder.
After trying to reduce the neck in one operation, unsuccessfully, I searched my parts box for an unused Lyman 310 tool, .270 sizing die. Since this die is too long to allow the .32-20 brass to reach the neck area, I cut roughly 1/2" off the length, and polished up the fresh cut. I have an adapter die that allows use of 310 Tool dies in a full size, 7/8x14 threaded press, so this was pressed into service. In effect, I reduced the case neck in two stages: roughly 0.314" to 0.277" then to 0.258". Getting a sizing die that's short enough is the tough part. I was lucky to have that old 310 .270" die. A .30 Luger die might work too, or a .280 die cut off to get the right length.
Again, after lubing the case, I SLOWLY resized the neck area of the .32-20 brass, allowing the die to size right down to the shoulder area. The .270 has a much steeper shoulder angle than the .25-20, but this would be ironed out during fire-forming. The key to this part of my operation was the right amount of lube and a SLOW stroke on the press handle.
Replacing the 310 Tool, .270 Sizer with my RCBS .25-20 sizer, with its decapping rod removed, I re-lubed the case and gently, with four short strokes, resized the case to its final neck diameter. Since the case head spaces off the rim, fire-forming is no big worry, and I sized only down far enought to allow the case to give me some 'feel' as it butted up against the shoulder of the chamber while closing the bolt. Here, as in the previous .270 sizing, the key seems to be: slowly forcing the case into the die, the right amount of lube to preclude shoulder wrinkles, and gradually setting the shoulder back, using four separate, short strokes.
I next resized the neck interiors with Lyman's "M" die in .258" dia., then seated CCI small pistol magnum primers.
I got 10 good cases, with no wrinkles or folds, no case body or neck splits either. I didn't lose a case with the above method. But the proof of the pudding is how they would shoot & the number of reloads I can get out fo them. For the minimal initial fire-forming necessary, I sized a cpl dozen 257420 gc boolits, and seated them over 7 grains of Bartett's clone of 4759. I've used this load before with good accuracy, & minimal pressure indications in genuine .25-20 brass, so I felt ok trying it here.
Off my porch rail, I got good case fill out, with the first shot, and accuracy was less than an inch at 30 yds with the iron sights on my model 65. Over the course of the afternoon, I reloaded these ten cases four times with no case losses. With any bottle-necked case, that's about my # of loadings before re-annealing. I'll give that a go manana. One note: Starline .32-20 brass seems to be thicker through the case neck region than genuine R-P or Winchester brass...could be the brass flowing forward during the re-sizing operation, or maybe it's just that thicker as a rule.
I checked several of the loading supplies outfits on the net, but none had Redding's .25-20 Form and Trim die in stock, and I wonder if they'd do the entire job without the two step reduction. For now, this procedure works for me, and I found that running the brass through was not as time consuming as my first attempts.
All in all, I'm happy to find an interim solution for the .25-20 cases I need to feed this rifle, and really pleased as well at finding a good plinking load on the first try. Accuracy wise, these cases are as good as originals. And a final note, I ordered 500 .32-20 cases from Starline this afternoon, to feed the .25-20 and an even older octagon bbl'd. M-92 in .32-20.
Best regards, Rod