So my R700 Varmint is a 1-12" twist, and it shoots best with 155's and 168's. I never had much success attempting to shoot 175's. Faster twist barrels favor heavier (longer) bullets. I think you will find the 168 SMK or Nosler CC will be a sweet precision bullet with your barrel. The 168 gr match bullet is the "do all" precision match bullet for 1-10" to 1-12" barrels. If shooting off a sand bag get yourself a rear "rabbit ear" bag to support the rear of the buttstock. After that it's all about trying powders and charges. I have excellent success with Win 748 , Varget and 2000MR with the 168's in 30 cal. When loading for the 30 cal semi's you want to makes sure you have the proper casing shoulder setback to ensure the cartridge fully chambers. A case guage is a great tool that guarantees you have the correct shoulder set back. You can also test by loading and empty resized casing and verify the bolt fully closes and locks. Good luck