I acquired a .221 Fireball specifically to build a 20 Vartarg, but after shooting it awhile I think I'm going to leave it be.
Instead I think I'll try a 20-222, and if it's "improved" with 30 degree shoulder I believe that is a .20 Vartarg Turbo. That way I won't have a problem with trying to find another Fireball follower and bolt with the correct ejector.
With the 20-222 it's just a neck-down from the standard 222, like the 20 Practical from the .223 case.

"I was born in the log cabin I helped my grandfather build"