I dabbled with a 300 win Mag a few years back. I had real good luck with a Hornady 208 gr ELD-M. My rifle had a bit quicker twist, I'm pretty sure your near optimum with the 178 gr bullet. I'm not familiar with "pills", are those custom made? Russian? or ?
Twist is a factor, but as important is the magazine length. Some rifles come with a 3.34" max length magazine, and that severely limits your bullet selection in your quest for accuracy. My rifle had a bit longish magazine, my LOAL was 3.42".
My 300 win Mag project was real budget, traded some tires and rims for a rifle, worked on it to "fix" the neglect and abuse. I just used some old H4831, never fooled with any other powder. 300 Win mag is a very capable caliber. My bore was not smooth, it did not like to shoot when clean. I just ran a bore snake through it with some oil on it after a shooting session, no problems after that.
I trimmed off about an inch and a half of the worst part of the barrel.