You guys that love this cartridge, I hope one day that you can have a custom barrel put on a rifle with no more than .070 freebore. Pac Nor has a short freebore reamer, and their 3 groove super match, 10T, shoots the 100's at 3850 and the 115's at 3600 with Fed 215's and R#22. I have seen the same with the Lilja and Krieger 10T barrels. The nosler 100g Partitions shoot half inch groups in this barrel, and the 100g Hornady btsp is my preferred bullet in 100g, never fails. 80g barnes ttsx at 4200 does not suck in group size(R#19), but I have only shot them for a short while.
My nephew is seriously recoil-sensitive. A gunsmith chambered an X Caliber 9T barrel for him with .020 freebore, and he is shooting the 110g Nosler Accubond and the Berger 115g VLD hunting at 3600 on a 25 or 26" barrels with groups sub 3/8" on three-shot groups. The gunsmith installed a Gentry muzzle break that throws a lot of the concussion Forward.
Recoil-sensitive nephew is now making some incredible shots, and no deer has ever moved at impact, DRT with him ALWAYS seeing the bullet impact on the animal...he is in love with his new rifle, on his third season now, hogs and deer.
I see no practical use in a Modern gun chamber having .300 freebore, .030 is much more practical in this cartridge for reloaders.
A friend used my zero freebore reamer to chamber for a heavy gun for shooting rock chucks. 30" Hart 10T barrel of his shoots the 100's at 4000 fps into tiny groups that are in the 1/4" area with three shot groups. I have tried to talk him into shooting the 85g Nosler ballistic tips and the 87g Speer, but there are none to be found.