is the double-barrel shotgun unlockable with proper gameplay? you know, like in the old days, where you couldn't buy achievements ... or is it only available for pre-orders?

i won't pre-order the game, because i want the game at day 1 from my retailer and he can't guarantee that i'll get it. so in case he won't have it, i'll get it at a different shop.

thanks for info

Like most preorder dlc, it'll most likely be available at a later date, but currently I do not believe there is any way of getting the gun without picking up the anarchy edition.