Oh that’s great news to hear Peterson’s is making 6 Dasher brass. I had the Norma 6 Dasher chamber so I kinda screwed myself. But I lucked out and it was easy to convert to the 6GT by just opening up the chamber. I’m very happy with the 6GT so far. I really like Peterson’s brass, I run it for my 6.5 Creedmoor hunting rifle.
I have 600 of the Peterson 6.5 Creedmoor brass and have been really happy with it so far. I didn't want to fireform and decided against the 6GT because I haven't had issues feeding 22BR out of the magazines I already have. Alpha OCD Dasher brass wasn't out yet, so I decided on giving Peterson a shot. Didn't seem like there is much to gain with using more powder in the GT over the Dasher.
The Peterson necks are thicker than Lapua, so the .275 neck ought to give me the clearance that I need. If it shoots 1/2 moa that will be good enough for me for shooting off of props and barricades.