New gun that I am loading for. Looking for the optimum powders people are using and what made them use it.

24" Barrel, client wants to use around the 160 grn bullet range out to 600 yards.

TSX is the bullet he usually goes with but will look at and try others as well.
Gun to be used on Texas deer hogs and varmints of opportunity.

My best friend had Jim Borden build him a 300 WSM earlier year. Jim says the two most accurate bullets in his rifles are the 165/8 CT and the 180 TTSX. My bud's rifle shoots in the .3's to .5's with the 180 TTSX and Rel 22.

You'll get many different responses as each barrel will be different. My 300 WSM is extremely accurate with Hornady 165 gr IB with RL-19. It doesn't group in my buddy's 300 WSM, and his 180 gr Accubond with RL-22 is very accurate in his rifle, but my rifle doesn't like it. You will need to try a few different powders to see which one your rifle likes.

I plan on having to try different powders just looking to see what powders some are using now and starting there. Hoping to eliminate as many as I can.

On your list of "to try" powders should definitely include Re22, 25, IMR7828SC, Ramshot Magnum, H1000, Retumbo, IMR4831.

My top choices would be Re22 and H1000.

H-100 and IMR 7828 are going to be the next batch. We tried H4831 heavaly compressed load but accurate and RL-19 slightly compressed and ok accurate.

Mine shoots just under .5 inches for 5 shots at 100 yards with H4831SC and 180 Grain TSX. I have shot groups in the 1.5 to 2.0 range at 400 yards with it. That is the load that I hammered 10 animals in Namibia with and a 6X6 Bull Elk with this year. I am shooting a Kimber Montana.

I load for three 300WSM rifles. All three luv Ramshot Hunter. I played around with Norma MRP this past summer and 165gr Partitions, very accurate and very fast. Gunna get me some more of this powder.