How do u like the the fatrat? i looked really hard it, but i liked the tac6 a little bit more than the fatty. Some of the guys over at barts bullets finally beat some straight ppc's with it...But damn near the same cartridge outside of case capacity.
Except for fireforming there isn't anything not to like. Lapua brass and it lasts long if you don't push the case, .059" flashhole, low recoil. My upper has been very reliable.
I try to make first round hits so I use temp insensitive powders, like H4895. Others don't care so much about that and use powders that give more velocity, like AA2520, which can give another 100 fps. I've learned to not try to make a little cartridge any more than it is, been down that road a few times, like when I had 105 Amax going 2915-ish out of a 26" AR-T40 in the mid summer. Put the rifle away and next thing I know it's mid winter before I shot it again. Thought my scope was broke because I was hitting low, mostly under a 10" plate at 600Y, chronoed and had lost 125 fps, lol. Yes I confirmed zero and had accounted for DA.
I tried 243 Win in the AR10 frame, I was surprised at how much more rifle movement there was compared to the 243wssm I had at the time, in spite of it being 2 pounds heavier, that heavy BCG coming back I suppose.
I hated that 243wssm upper because the brass was horrible (worst I've ever seen) as well as it being unreliable and inaccurate, but the upper was a Olympic Arms which isn't known for quality.
The 243 Win was okay but in a 20" barrel I was only getting 2800 fps with 105's, the 243wssm was 150 fps faster in a 24" with the same bullets.
I've had problems with 22 cal Hornady 88's not making it to the target in my 223AI so I'm reluctant to go 22 cal in spite of the higher BC so at this point I'm staying with 6mmFatRat.