You could just try some cast in 7mm as Phil is doing. Keep it in the 'family' :)

2400 is a very common powder for cast. I'd have tried it by now but I don't have any. For the mid range loads (1500-2000fps) it seems to do really well.

Cast Boolit forum has a ton of folks experimenting with cast coatings and lubes. Moly coating has been tried in several different ways and does not seem to make a lot of difference. Having said that, my bullet lube uses Stalube Extreme Moly grease as the lubricant and beeswax as the carrier. HBN I am not sure. I have not seen any mention of it. The two 'big' coatings used these days are Powder Coating and HiTek. Both are baked on. HiTek is a proprietary formula so I don't know what is in it. There are several companies who sell coated bullets that use HiTek.

There was a lot of cast experimenting in the BR crowd back in the 80's. I remember a series of articles about using moly coating. The results were ok, but, not better than standard lube. They also experimented with polyethylene wads instead of gas checks. Those did work well, but, you had to use a case with a relatively long neck (IIRC they were testing using a .32-40 case). There is still a Cast Bullet class for plain base bullets.

FWIW, the biggest area of cast bullet performance is the casting of the bullet itself. Making a bullet with the fewest voids/flaws. Not as easy as it sounds. From what I can tell the most consistent results come from ladle pouring. Of those the ones that use the Lyman ladle and hold it against the mold do the best. After that, temperature control is key. I use a bottom pour pot as I like the convenience, but, I also cull out quite a few bullets. Some of the 'pickier' shooters will only keep 25% of what they cast. My 'control' is bullet weight. Bullets are sorted to 0.1gn and I only keep the ones on the high end of the curve.

.300 BO is a popular case for cast with the AR crowd. Most of them are using faster twist barrels so they get mixed results (and they are trying to cycle the action) It does seem to be a good size for light bullets. Reminds my of my old .30 Herrett.