The Jackhammer Experimental Unpacking Cannon, is a major experimental introduced with the Infinite War Battlepack DLC. The Jackhammer is a short-range cannon, being able to lock itself into position and unfold a large cannon used for arced bombardment.
While being used as a short-range cannon it is completely immobile, being vulnerable to incoming enemy units. Yet, while being mobile, it appears to have no form of weaponry what so ever, and cannot defend itself.
The Jackhammer has a remarkable resemblence to Halo Wars' Cobra & Rhino unit, as they both lock down in a similar manner and turn into powerful artillery-like units. The jackhammer is easily able to take down multiple units killing between 5 to 12 units if in close proximity and excels at covering choke points (Markon's bridge, for example).
The Jackhammer is probably best explained by comparison to the Fatboy II, a UEF Minor Experimental Land unit.
After all training upgrades, the Jackhammer has 60,000 health, more than some other Major experimentals. By comparison, the Fatboy II has just over 14,000 health after all training upgrades. Jackhammers cost roughly 20% more mass and energy to train, but with over 4 times as much health, they have a much better Mass to Health ratio.
Jackhammers take only 30 seconds longer to train than Fatboy II's if unassisted.
Jackhammers move just as fast as tanks, slower than assault bots and considerably faster than the Fatboy II. When a large mass of enemy units is inbound, pack it up immediately and you may be able to get it back to cover before those units can catch it.
The Jackhammer's gun fires a single projectile 90% as far as the Fatboy II. Despite being a single shot, the Jackhammer's projectile does massive splash damage, enough to destroy level 3 adjacent energy generators in a single shot.The Jackhammer fires once per 5 seconds, Fortified Artillery fires once per 2 seconds. The Jackhammer's DPS is ~65% higher, but will actually work much better against buildings than the Fatboy II, due to the splash radius being so large. It does not track its target, however even Assault Bots cannot move fast enough to not be caught by the splash damage. Jackhammer's muzzle velocity is 30 vs. the Fatboy II's muzzle velocity of 25.
Jackhammers are less effective by themselves than Fatboys, as they cannot kite return fire and are completely vulnerable to missile launchers, teleporters, jetpacks and air units (not to mention the fact that enemy ground units can be micro'd to close the distance without taking any significant casualties). Situationally, kiting may not be necessary, but use of p-shields and other fodder to protect the Jackhammer is typically essential. A stranded Jackhammer is a defenseless Jackhammer.
Jackhammers are highly effective defense units. Their range falls squarely between Heavy Point defense and short range artillery. Jackhammer range: 90, Fortified Artillery range: 115, PD range: 40, and they can be used to "thin out" even the heaviest ground force, lightening the load on your stationary defenses considerably. If placed within range of choke points with proper AA and repair support, a Jackhammer or two will deter light ground incursions. The new UEF Combat Engineer and p-shields are ideal support units for this experimental.
Jackhammers are extremely effective against grouped p-shields. Due to splash damage calculations, all p-shields that are hit by a Jackhammer will collapse in one or two shots, regardless of the degree of overlap.