@ Changling,..
And made with,.. a smidgeon of, Body Taper to feed well and the 30* shoulder, being set back, to obtain a little longer Neck, THEREFORE, it keeps, the Burning Powders "Turbulence Point", BACK inside, the Case FURTHER than say, a .243 Win., so it's NOT "torching" the Throat as much ! The Case allows, GOOD case capacity to allow the USE, of Colder Burning,. VhitaVouri N-160 and N-165 and ALL these "attributes" allow for LONGER, Accurate, Barrel Life !
IF more, Power / Velocity needed, check out, the 6 mm SLR. Both of these Cartridges, REPLACE "duplicate", the .243 Win ( use wise ) and have ABOUT, 50% more useful, Barrel Life ! Hope this, Helps !
I credit, David Tubb as the OFFICIAL and BEST ,.. "end USER" if not,.. the actual designer !
I'm gonna build, my next Varmint Rifle, using, a L-H Rem 700, short Action and the 6XC case with, a 1-12 Twist to shoot 55's to 80 grain, Bullets. YUP,. they ARE that,.. GOOD !