Thread: Quietest firearm possible?

I've been thinking, what would be the quietest you could make a firearm, just for fun? I've been toying with the idea of getting a pistol calibre carbine of some sort for a while now, mainly for small game, but also to suppress and play around with subsonic loads. I'm guessing some of the quietest rifles ever were the De Lisle carbines; owing to it being manually operated, using subsonic ammo, and the over-sized suppressor. But does anyone know if having a ported barrel bleed gas into an integrated suppressor would make it quieter if the projectile was already subsonic to start with? Does anyone know the lowest velocity you can load an still have the projectile exit the barrel each time reliably, I'm assuming the slower; the less noise. Also, would cast lead bullets be quieter than jacketed ones? What about the firing mechanism; it seems like the loudest part of firing the De Lisle, would an external hammer like on a break-barrel or lever action be any different than a firing pin inside a bolt action? Are all cartridges created equal for subsonic loads or are some just inherently good? I don't really want to get into wild-catting but I know the Russians have a cartridge that is essentially a 7.62x39 necked up to 9mm for launching heavy bullets sneakily. Right now I'm thinking of picking up a cheap single shot break barrel (for safety so I can check bullets are not stuck in the barrel after each shot) in .44 magnum or similar, sticking a maximus suppressor on in and loading some subsonic rounds using Trail Boss. Does anyone have any ideas?