A lot, I have made a weapon creation system that even allows the players to create their own and share them in the Steam workshop. You can try the current Steam Festival Demo and there are several new guns available.
The BLASTRONAUT game is currently in development and it has not been released in Steam Early Access yet (but it is the plan). The current Web demo that you can see in Itch.io was released more than a year ago, and I think it only has 3 or 4 weapons, I don't really remember how many exactly. At the current moment, there is also a Steam Festival going on, which I have made a new Demo with multiplayer, crafting, enemies and other stuff. It also has more weapons. I recommend trying this new demo if you are interested.