It just needs much more ammo. Atm with only a 6 round magazine it's in direct competition with the standard shotguns. Imo the Jackhammer USP should be a bigger mag, longer effective baseline range and the 3 shot burst but at the expense of the instant high damage of the other shotguns.
Been using it as my main heavy weapon, I absolutely love the extra range it gets over the standard shotguns. I don't see a problem with the guns mechanic, I just often find myself running back to a resupply station so extra reserve ammo would fix that up. Gun is great at mid-range and average close range, I just snipe SMG players in the head with it if they want to engage at mid-range. Just needs to be used a little bit different from your standard run and gun shotgun.
The sweeper does better you must be on drugs if you bought the jackhammer if you already had the sweeper/piston.
nah it doesn't have the same firing characteristic as the jackhammer which is the whole reason I enjoy playing with it. neither does the piston used to use it almost predominantly but now run the jackhammer, the piston feels a bit tinny at mid range engagements.
