Quote Originally Posted by Westcliffe01 View Post
My understanding is that you form the brass by firing it in the improved chamber.

Yes, the hallmark of a true improved chamber is the ability to fire the parent without any changes. Cartridge head clearance, or the lack of it in this instance, is from the breach face to the neck-shoulder junction with a crush fit typically in the .004"-.006" range.

A few examples smoked to show how head clearance is established on the junction of the parents for firing/forming


L to R, the 22-250, 250 and two wildcats, the 270-08 and it's improved version. All three require unique length gauges.


Not knowing your experience with improved cartridges is why I suggested using virgin brass. Sometimes improved cartridges get a bad rap due the brass being used, split necks and etc, a result of work hardened brass. Go ahead and use your one fired brass. If you run into problems you may need to anneal it.

Bill