Using Alliant's max load for R15, under a 170 grain Hornady interlock, I got my best group, a true 3/4" group. Yes, a one off, but spectacular for a 20" carbine none the less.
It's a very hot load in my rifle. I was just playing with it, and have yet to get back to see if I can work up an accurate load with less pain on the old rifle.
I went to look up the load, but they have pulled it from their site. I don't have access to my records right now, so that will wait.
H4895, W760, W748, R7, BL-C(2) and H4198 have all worked well for me in the past.