While I'd like to shoot 34g slugs, I personally feel like the 600mm is most comfortable shooting roughly 30g or less slugs (with the exception of Altaros ATP Kings). I've found these to work well with an OEM Panthera. Altaros 31g @ 920 fps H&N 30g @ 970 fps H&N 27g @ 980 fps ZAN 33g @ 950 fps...