Up until today was the 300win mag, but, Ihelped a buddy out with a load forhis 300 ultra mag today, ended up with 100.5gr of Rotumba and a 180gr Hornaday SST, WOW!! what a shooter. We didnt have a chrony set up, but downrange accuracy was sub-moa, three shots in one ragged little hole, it definatly impressed me from the first one I shot a couple years ago, after the second shot I handed it back to the owner and told him he could keep it!. But in all reality, Ill stick to my 300win mag!.