The J-27 is designed to transport dangerous munitions and missiles from a rear supply area to BattleMechs and infantry units in the field. It was the backbone of the Star League's ordnance service prior to the League's collapse, and many of these transports are still active in the Successor States.
         Designed for rear-area operations, the J-27 has thin armor and so makes an explosive target. The munitions it carries are not protected in any way, exposing the transport to danger every time the vehicle nears the combat zone. Extreme heat can also pose a grave threat to crew members of the J-27.

         Even though the J-27 plays a crucial role in combat by providing front-line troops with ammunition, such duty is usually considered punishment rather than a privilege.  
         The J-27 can transport three tons of munitions in its front, tracked cab. Its wheeled trailer can carry another eight tons of ammunition. The front cab usually supports long-range missile reloads, but the missile rack can be removed in minutes to take on other munitions.
         For the most part, the personnel of J-27s are losers from the infantry. Some units, especially those of the Draconis Combine, are considered penal units. Military convicts are offered the choice between a firing squad and duty on the J-27. The majority choose the firing squad. It takes two people to drive the slow transport; the third crewmember is in charge of securing the munitions and manning the single SperryBrowning machine gun mounted over the cab. The mount is designed so that it cannot fire low enough to hit the supplies in the cab or trailer.
         One major drawback of the J-27 transport is that the trailer can only be detached from the cab manually. When a J-27 comes under fire, the load checker must detach the trailer to make the vehicle a smaller target. Unfortunately, in most cases he must crawl across the cab's cargo and down the back of the cab to disengage the trailer while the vehicle is rumbling across the countryside and taking enemy fire.

         J-27s survive throughout the Human Sphere, some left behind by the Star League and others built by other corporations since those days. Easily the single most recognizable class of ammunition carrier, most soldiers have at least seen them in action.