Let me see if I can quote his posts then:
I had spoken with Clay and James W about my PC Kearin taking an interest in modifying his warhammer using his skills with both smith’s and tinker’s tools he would like to present his work to the federation for others (who wish to do so) to use, granted it is approved by the DM’s. A brief rundown of the modifications, the flat face was removed and the internals of the hammer had the center bored out and fitted with a mechanism that functions like a revolver cylinder, to use the new (experimental) features an individual would have to load 3 explosive viles(max) into the cylinder and secure the flat face back in its original position, each hit/critical miss with this weapon would expend a vile on a successful hit it would do 1d8 bludgeoning damage and 1d6 force damage, on a critical miss the vile would explode and deal damage to the PC wielding the hammer doing 1d6 force damage and also knock them prone, I had designed it that a critical miss with this weapon would kick in on a natural 5 or lower giving it a little more danger to use than any other weapon the federation currently has in its possession. Any feedback would appreciated and any alterations can be made to better help it fit in at the DMs tables
I also took the time to create the item on DnD beyond since i know alot of the players use DnD beyond
So currently kearin has proficiency in alchemy tools i had gotten the idea of combining the metric ton of dynamite he had received some time ago into a more fun, yet also more risky style of combat. Personally I like dynamite as an item but i personally feel that it is a little too over powered for were he is right now (3d6 Bludgeoning) on a failed save from a 60ft distance so i had gotten the idea of just breaking down the dynamite into vials or mini dynamite if you will that deal 1d6 damage each and then combined them with the warhammer getting the idea from the boomhammer in Bloodborne if anyone is familiar, changing the damage type to fire would also be perfectly fine. I had thought about just having the weapon knocking enemies prone instead of doing the 1d6 but I feel that a weapon that could potentially knock an enemy prone every round could be rather game breaking considering that while an enemy is prone all attacks have advantage. I dont personally know what i would expect it to be considered between uncommon/rare but i wouldn’t complain about whatever the DM’s decide if it is ruled to be allowed.
also heres the published link for the Hammer