In general, "chemical slug throwers" is too big a topic.
It might be nice to have a better rundown of the more advanced (TL 8+) firearms and what they can do that modern firearms can't. But most of the "slug" weapons are pretty familiar in design, so probably don't need a lot of expansion beyond what the CSC gives us.
A discussion of fancy high-tech "upgrades" like smart weapons and ultra-sophisticated targetting gear might be more interesting.
And of course the laser guns, but those are already on the list. (yay!)
As if you don't already have enough ideas of your own

, I'll throw in a few more:
A Combat Armor or Battle Dress book would be nice from a "gun pr0n" perspective. Battle Dress can be a big topic though.
Space Suits could also be an interesting addition to the line. Come to think of it, I'd be more interested in this one than the armor ones, simply because I don't generally run mercenary games.