Well, after lots of tinkering with bullets and powders, I found a load that my .300 likes: 180 grain Hornady Interbonds and Hybrid V powder. The only problem is, now that I've loaded 50 rounds to keep for hunting purposes, I have no more interbonds as it was a box I bought a while back to try out with various rifles and cartridges. Now that I've found something to use them in, the bullets themselves are of course unobtainium. Well, since I have 180 grain TTSXs lying around, I will try them with the Hybrid V. Maybe that will be the magic powder for them as well.