6 BR at 400 yards would be overkill just a joke I told you I also like small cartridges. I shoot a diamonback right bolt left port drop port 6br no neck turn .98" free bore load and shoot no fuss. You will love it for 400 yards you dont need 105's but they will work fine. I shoot 107's as far as I can launch em. The fox was at 670 yards and Ive shot too many G-Hogs to remember. I also cull deer with it but you have to be careful as shots get longer. Go for it, you will love it.