I shot 150 grains of 777 pellets in my 1st ML which was an Optima using 348 grain Powerbelts about 5 years ago and they were all over the place. I now know that was too much for PBs but I no longer use them and shoot an Omega with 2 pyrodex pellets and/or 90 grains RS with SWs but may try 300 grain Barnes Expanders.