So, the rules for Empty Quiver Style state
"If you have the Stabbing Shot feat, you can use it with a crossbow or firearm, substituting a loaded bolt or firearm ammunition for an arrow."
First question, mostly for RP/Flavor's sake: when it comes to using a firearm for this attack... you just... push the bullet into the enemy with your hand? this sounds messy with an early firearm's ammunition consisting of a bullet and loose powder...
Second question: is the bolt or firearm ammunition expended after this attack? because in the case of the crossbow or firearm and the bolt or ammo in question needing to be loaded after your first attack your weapon is no longer loaded... in the case of the crossbow if the bolt sticks out past the end (which I'm pretty sure it doesn't) I could see it being stabbed into someone like a bayonet, but a firearm's ammo definitely doesn't stick out like that...
third question: or is it basically having you fire the loaded bolt or firearm ammunition for this?