Which Neck Sizer to use

[Trickymissfit]

Dunno what would be the very best. The best product I've used for case sizing is Imperial Case Wax. I could be surprised, but I don't expect this process of setting the shoulder back to be all that difficult.

And taking the necks down will be very simple provided no individual step-down process is too large. If the case neck shoulder collapses, you'll know it's time to add an extra step to the necking down process. Any pistol resizing die that you have on hand might make the neck resizing process more gentle. A 38 Special or 357 Magnum case resizing die might be an option for the first case neck reduction step. That would only be 0.018" step down in the first process. That's a very common die. If you don't own one, perhaps a friend does? Less is always best. I'd try that and see if works well.

Then move on to the 338 RCM die for another 0.019" reduction. That would turn the one-step process into a milder two-step process from .375 to .338. When I have to neck down wildcats from parent cartridges, I use anything I already have available (meaning no additional cost) to size down in smaller steps.

Another means for a two-step process between .338 and .308 could be a 325 WSM (.323") full length resizing die, if you have no-cost access to one. I do believe you'll be able to go from .375 to .338 and from .338 to .308 with just one-step each, and wouldn't spend money to break those down into two-step reductions. But if you have a no cost option to size down through a four-step process, like .375 to .357 to .338 to .323 to .308, then that's what I always try to do.

I have a relative that owns a gun shop and I have been known to borrow used reloading dies (pistol or rifle) from whatever is available there in the shop to progressively size down case necks. Which of course is helpful. But sometimes I borrow various dies from a friend, since they're only for one-time use.

I've got one case that I move the shoulders back .31", and do it in two steps. The only reason I have to do this in two steps is that I have to trim the necks back with a jeweler's saw. Use nothing but Imperial Die Wax. I do a deep anneal before ever starting starting the first operation. Another case that is similar, but longer has to have the neck opened up from 30 caliber to .375, and then brought back down to 35 caliber. I've lost maybe a half dozen cases over the years. Another I've been doing is .225 Winchester brass necked up to 30 caliber and then moving the shoulder back quite a lot. This brass gets annealled twice during the operations as it seems to really be prone to work hardening. I take this all the way up to .338, and bring it back down in two or three stages. Cases that are hard will often split necks during fire forming
gary

 

[elkaholic]

I've got one case that I move the shoulders back .31", and do it in two steps. The only reason I have to do this in two steps is that I have to trim the necks back with a jeweler's saw. Use nothing but Imperial Die Wax. I do a deep anneal before ever starting starting the first operation. Another case that is similar, but longer has to have the neck opened up from 30 caliber to .375, and then brought back down to 35 caliber. I've lost maybe a half dozen cases over the years. Another I've been doing is .225 Winchester brass necked up to 30 caliber and then moving the shoulder back quite a lot. This brass gets annealled twice during the operations as it seems to really be prone to work hardening. I take this all the way up to .338, and bring it back down in two or three stages. Cases that are hard will often split necks during fire forming
gary

I've done some annealing before fireforming with certain brass to form my Sherman case because there is a considerable amount of stretching. Have you found that you have to be very careful to only anneal the neck no further than the shoulder when you do this so you don't collapse the case? This would be when you don't have full support on the case body as would be the case when you are blowing taper out of the case body......Rich

 

[Trickymissfit]

I've done some annealing before fireforming with certain brass to form my Sherman case because there is a considerable amount of stretching. Have you found that you have to be very careful to only anneal the neck no further than the shoulder when you do this so you don't collapse the case? This would be when you don't have full support on the case body as would be the case when you are blowing taper out of the case body......Rich

That would depend on where the shoulder ends up at. If I'm moving it a lot, then I anneal into the shoulder. But if it's a small amount I don't bother. I always do the necks before I start. If your trying to push the shoulder back, and it's unsupportted; you might have problems. Have never tried to move an unsupportted shoulder, but can see trouble. Years back I used to have access to a Star CNC cutter grinder, and cut a few roughing reamers with it. This would be the way I'd go if I were doing it right now. If you have a lathe with a taper attachment, then you can simply turn something out of a piece of A2 drill rod. It's easier than it sounds, and the stock dosn't change from heat treat
gary