Molybdenum disulfide is a dry film that has the property of embedding itself into metals and staying there.

I went down this road. In the end, not worth it to me. It works. A properly moly'd barrel shot with a moly'd bullet, you can gain 100-150fps. But, you have to venture out on your own with load data. Go past max and understand the signs of trouble. Carefully chrono'ing your load. It cuts down copper fouling. And an added benefit of repeatable cold bore performance. I can vouch for this.

Sounds groovy don't it?

Here is the bad news. Its hydroscopic. Sucks up moisture. And if you remove it every range session, then it takes several shots or "moly treating" of the barrel to get back to where you was before. So most guys leave it in the bore. Don't clean but every 100's of rounds to get the benefit. Also, you get buildup every few hundreds of rounds and get a moly ring, which causes huge pressure/velocity spreads. Sporatic performance. Its messy, and you need a separate tumbler.

I just got to the point, where I just wanted to buy bullets and shoot. I didn't like having these heavily fouled bores, and worrying if it was pitting my barrels.

Another tip, make sure you get the stuff made for guns. Some out there, used in the machinery world for large bearings, can and will pit your barrel.