A buddy made a 6mm on the 22-250 case 30 yrs ago. It became the 6XC.
To be honest I am certain there were a bunch of guys who made that cartridge even earlier.
Look at the guys that necked the 284 Win up and down when it first came out in 1963.
while no company stole my glory, I have made a few that I am not aware that anyone ever made:
Took a 30 BR reamer and cut deeper to make a 30 BR front headspaced as a 308. 30 degree shoulder, less body taper, thin neck wall
A 358/338 RCM.
While not exactly a new round used a LA with a long throated 338 RCM to shoot the 300 gr Sierra and later when it came out the 300 gr Berger.
Last edited by Azshooter; 09/25/19.
