Found this combination to be very accurate in my rifle.
Savage model 12 single shot, 24 inch stainless fluted bull barrel, 1 in 12 twist rate I think.
CCI 200 primers, 55 grain nosler ballistic tip boat tail, 37 grains of hodgden H 380. Loaded to 2.50" total length.
Shot today and got a .65" group at 275 yards with 3 shots.
The 12 twist rate is perfect for the Sierra #1365 bullet with a .8 factor. It might or might not shoot the new 53 grain Vmax that has a .29 b/c (it's very close to max). I shoot the Sierras with IMR 3031 at 3500fps to 3550 fps (load came out of an old IMR booklet). Seat the bullets within .002" of the lands, if not just barely touching them. The rifle has shot a lot of low twos, and a few high ones in a Savage 112BVs-s (the old one with the blue reciever). I have another 112 just like it but not the single shot, and it will do high twos and low three on a regular basis with the exact same load.
I have tried H414 and H380, but didn't group as well. Want to try 2015BR, as it's almost an interchange for 3031 (one is slightly faster)
I tried that 60 grain bullet, and the smallest groups I could get were around 5/8th's inch. But with a .27 B/C it should stabalize. I've not tried the powder you used. H414 might be worth the try.