Remington sps with varget and 155

Give Dan Newberry's OCW method a try. OCW Overview - Dan Newberry's OCW Load Development System Using this method on my Savage w 1 in 10 I settled on 46.5 gr. Varget for 150's and 46 for 155. Follow Dan's instructions and you'll safely be able to work up and I'd bet you'll find a node above 45. Varget seems to like being run on the near max or slightly compressed side from what I've experienced and with no pressure signs - in my gun.
 
You sure its a 1:10 twist? SPS Tacticals usually come in 1:12 - not that it should make any difference with 155's. My SPS tac loves 168 / 175 SMK's as well as 185 Scenars. Never could get on with the 155's, plus you're not as likely to get the velocity to get the most out of 155's with a factory 20" tube. The 175's and 185's perform well at 1000.
 
Just to verify the rifle, find yourself a box or two of Federal Gold Medal Match. I'll assume .308 or 7.62x51. Yes, they have both. Easier reloading the .308, than the 7.62x51 but either works great.

Then if those work well, I would just try a few different powders and work around until you find a good group for your rifle. Or use, as suggested, the OCW method. Personally, my rifle loves the SMK 175 gr HPBT. But of course, most rifles do. :)

Good luck.
 
I had trouble getting 155's to group well in my model 700 tactical, but I'm having good success with 168's and 175's. 20 inch, 1in 12.

Tried 4064, h335, Varget, 8208 XBR powders, nothing to work in the remington. But they group well in a Win 70 with a 26" varmint barrel.

Just my 2 cents.