How often do you switch between loading the two cartridges? If I ever had a spacer I misplaced it a long time ago. From your setting for loading .38 special just back the seat/crimp die out two full turns and you will be very close to where you need to be for .357mag. I always make a few fine adjustments anyway and wouldn't count on a washer putting me spot on.
The difference in length between the two cases is 0.135" if all are trimmed uniformly. The die is threaded at 14 turns per inch.
0.135" x 14 tpi = 1.89 turns.
After backing the die out 2 turns you will be running it back about 1/10 of a turn for fine adjustments.
An easier way is to start with the die and seating stem backed way out. Put a previously loaded cartridge of the type you want to load on the ram and raise it to the top. Screw the die body in until it firmly contacts the top of the case. Snug down the lock ring. Screw the seating stem down until it firmly contacts the top of the bullet. Done.
I have a dummy cartridge made up for just about everything I load and I use them for this purpose.
Proud member of the NRA and Texas State Rifle Association. Registered and active voter.
Last edited by Sport45; October 26, 2012 at 08:56 AM.