So some of you have probably been down this road before and have tried either successfully or unsuccessfully to form 25-20 brass from its parent case the 32-20. I've read about everything I could find online some people saying to use RCBS dies , some saying to use a Redding form any trim die first then full length size them , some anneal the brass some don't. So after having tried using my die set to form them and basically ruining 90 percent of the brass I tried I found an interesting video showing someone who made their own forming dies from a couple 7/8 -14 bolts that fit reloading presses , drilled out the ends one with a 7.5 mm drill bit and one with a 7mm drill bit , he then proceeded to run a brass case up into the 7.5mm drilled hole , then into the 7mm , then into his full length sizing die and voila perfectly sized 25-20 brass !
So since I'm a machinist and have a lathe at my disposal I threaded a length of material to 7/8-14 , cut it in half , drilled out the ends with both sizes , drill bits in 7 and 7.5 mm are available on Amazon, I also chamfered the outer edge to the exact same angle as the brass shoulder angle. Run them up into the 7.5 till they bottom out on the shoulder , then the 7mm , then full length sized , I use a very sparse amount of imperial sizing wax and never put any on the shoulder or there's a risk of ripples in the brass , I basically just have a hint of wax in my fingers and twirl the brass before sizing it. And out of 200 I've done so far I have perfectly formed brass with ZERO failure rate !
Easy as that!
So since I'm a machinist and have a lathe at my disposal I threaded a length of material to 7/8-14 , cut it in half , drilled out the ends with both sizes , drill bits in 7 and 7.5 mm are available on Amazon, I also chamfered the outer edge to the exact same angle as the brass shoulder angle. Run them up into the 7.5 till they bottom out on the shoulder , then the 7mm , then full length sized , I use a very sparse amount of imperial sizing wax and never put any on the shoulder or there's a risk of ripples in the brass , I basically just have a hint of wax in my fingers and twirl the brass before sizing it. And out of 200 I've done so far I have perfectly formed brass with ZERO failure rate !
Easy as that!
