Not with a 20 cal if you want decent straight ammo you can bed the stem though to fit the intended bullet.Any 223 seater should work, LEE, RCBS, Hornady, etc.
RCBS doesn't sell replacement seating stems anymore for the old version of the competition seater with the window.Modified older version 223 RCBS Competition seating die w/20 cal stem and 20 cal bullet guide. The loading window makes loading those dinky bullets much easier.