Level 2 (ie. Marlin loads) are completely safe in the BC. Check out the nef forum and you'll find a lot of info. My current load is 36 grains of H4198 behind a 405gr hardcast. It's below level 2, but it gets your attention (at about 1700fps) and leaves almost no powder residue in the barrel. You should be able to get a bit over 2000fps without exceeding level 2.