17 Mach IV Forming???

[Nelson]

I just got a set of RCBS form dies for the Mach IV and am wondering if I should set them to make contact with the shell holder or if they should be set up differant. I have been using the Bullberry style form die with my 17 Jet and have had great luck, but I wanted to know the correct way to use the RCBS Form dies with the Mach IV. Thanks, Nelson

[Ackman]

If you're forming .221 cases, dies will be close to the shellholder but not necessarily touching. Don't go by the shellholder....set the dies according to the chamber. It takes a bit of trial and error. The MIV case blows out some on the first firing - like an Ackley Improved - so you want some crush on the case. Set the dies to where you feel a bit of pressure when closing the bolt. That "crush" you feel isn't the whole shoulder hitting, it's just the neck/shoulder junction.