Yes, "single digit" SDs are a goal but seldom achieved consistently with 10 shot tests. Also with some cartridge they are more easily obtained. A 300 WM in a rifle with less than a 26" barrel is not one of those cartridges. I have chronographed (10 shot tests) the best of several different very high quality 300 WM loads out of M24 rifles used for very long range shooting. The ES of those loads averaged around 40 - 75 fps. Those ESs with the bullets used at 300 WM velocities for those bullets can correlate to less than 1/2 moa (5") of vertical dispersion at 1000 yards, usually much less.
What I'm telling you is based on actual chronographing a lot of loads in many different cartridges and guns since '74. In the last 13+ years, since I started pressure testing, I have tested close to 3000 different 10 shot tests. Occasionally, actually very seldom, is there any cartridges that consistently give SDs in the single digit much less any ESs. Even then, of those rare instances, it is seldom repeatable. Low SD and ES with some cartridges can be done but to expect consistent single digit ES out of a 300 WM.......the odds are better at winning the lottery or getting struck by lightening.
Out of my M70 Target rifle in .308W my LR match load of the 175 MK over Varget for 2750 fps give SDs of 16 - 20 fps with ESs of 40 - 60 fps. That SD and ES range is pretty much the same out of my Savage Competition M12 with a 29 1/2" Palma barrel on it with the best of Federal match loads or my own match loads.
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Out of my M70 in 30-06 the last test (10 shots at 300 yards) of my LR load [178 Sierra MK over 100% load density of IMR 4831] averaged 3050 fps with a 12 fps SD and an ES of 36 fps. The 300 yard ten shot group ran 1.6" or just over 1/2 moa.
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In your 300 Win mag with jacketed bullets continue to weigh the charges. Use a powder that give the best performance [velocity and SD/ES] at as close to 100% load density as possible. Also the bullet weight should be compatible with the twist and powder used. Truthfully the 168 gr bullet is a bit on the light side. A 178 to 220 gr match bullet would be a better choice.