Originally Posted by Three-Five-Seven
The best thing I learned on this site is to take the expander ball out of the sizing die for 357 sig. You can substitute the decapper from any straight walled set, as they don't have expanders.
You can get a chamfering tool just about anywhere, but an ordinary countersink bit will work just as well. When you take the expander plug out of the sizer, you really must chamfer cases to ease bullet seating.
If you continue to load with the expander ball in place, you are creating a potentially dangerous situation. When your bullets set-back in the case, due to insufficient neck tension, it can cause pressure spikes in your loads. These can actually be serious enough to blow your pistol up. So, clean up your act -- pronto!
This really depends on your dies. RCBS dies have had problems since they were introduced. They assumed it would load like a rifle, hence 2 dies, it really does not. It loads like any straight wall pistol case. I load 357sig on Dillon carbide dies, expander in place, slight flare w/ the powder through expander, good taper crimp. I have no setback isues using proper bullets. Full length sizing is turning the die down all the way until it touches the raised shell holder. You may have an early, poor set of dies from RCBS. They do not sise the case for proper headspace on the small shoulder. I would suggest the Lee dies w/a carbide 40 sizer
The 147grXTP just works, if your die setup is perfect. Measure the expander mandrel, it should be undersized, about 0.350" works. You can chuck it into a drill & polish it down. It sounds like you are pretty new to the reloading thing. I woudl put the 257sig aside until you get some add'l. exp. loading the 40s. You can mess up pretty badly trying to load 357sig w/ no experience. Your questions tell me you have not read a reloading manual or two. Research, there are no internet shortcuts.