I am confused reading your post. Is Superperformance (HSP) the only powder you had available ? There are dozens of "suitable" powders that will work fine in a 308.
Commercially available HSP is quite slow and I have found you can exceed 4831 velocities in slightly overbore cases like the 25-06. I get 4000 fps with an 80 gr TTSX in the 25-06 (30" bbl)
Hodgdon says:" Superformance delivers striking velocities in cartridges like the 22-250 Remington, 243 Winchester and 300 Winchester Short Magnum. Velocities well in excess of 100 fps over the best published handloads and even larger gains over factory ammunition! Because this propellant is tailored for specific applications, the number of cartridges and bullets is limited, but where it works, it really works! "
I'd guess it is too slow for a 308 as Hodgdon lists no 308 loads for it on their website, nor does Barnes. Even with a 220 gr solid, Barnes get the best with BL C-2 which is far faster than HSP.
Hard to beat 748 and 760 in a 308 with 150-165 gr bullets and they both meter +- 1/10 gr
good luck !
