I've been trying to get this trophy for a while and after looking around on the internet i found out that without the piano gun pre-order dlc this trophy is impossible to get . 
now I know that it will soon be on PSN (once the store is back up that is) but I just find it slightly shady and annoying that a trophy relies on someone having pre-order dlc from the right shop

You can get it without the piano gun. You're probably missing the .44 magnum.

@CL60: is that the gun at the start of the game? if so is the only opportunity to use it at the bank heist? cause i only used the shotgun for that scene

i just did that case and used the revolver but the trophy is still missing?

well the tommy gun is the piano gun isn't it? it's a tompson with a box ammo 
if the tommy gun is in the game i couldn't find it

The tommy gun that bares resemblance to the piano gun can be found at the end of "The Fallen Idol". I just got the achievement like yesterday, the two dudes near the first barrel you have to shoot should have some.

Roscoe and friend is the throphy for using all guns to kill dudes? then to complete it you need to use the flame thrower at the tunnels , that is when I got it .... let me check
 
Edit: Yep you need to use the flamethrower also and I didnt use any DLC packs or anything like that

thanks for the help i finally got it when jack attacks lelands house