B WOOD, get on the phone and call E.Arthur Brown Co. at 1-800-950-9088 and order a copy of 'Shooting Steel'. There's a whole section on the Seville 375 SM,pluse lots of load data Some loads listed are: Hornady220gr.jacketed H-110,23.5gr=1623fps IMR4227,23gr=1618fps H-4227, 21gr=1305fps The last load was chrony from a DW,it will do 1600+ out of your Seville! Like Marshall said, AA-1680 is great in the 375 SM. Its the best for full power loads in my 445, but H-4227 is more accurate. I didn't see any 375 loads with AA-1680, but it shouldn't be to hard to figure out a startingload. Best bet would be to call Sierra if your unsure. I hope this helps. Royce