A 1:9 twist can be a bit of a gray area, since stability depends on more than bullet weight alone—bullet length, construction, velocity, and atmospheric conditions all play a role. The fact that your 69-grain MatchKings are showing clean holes is a useful observation, though.
I’d be cautious...
Those mixed-weight bullets would probably be fine for practice if someone is already set up to inspect and reload pulled components carefully. I'd just sort them by weight before loading so you're not mixing 300 gr and 305 gr in the same batch, especially if you're working up a load. sports...