Yeah, I've got to agree with Essex on this one. The M249 is a LSW-type weapon system. It has no defined standard state and can be both mounted or handheld. Regardless of what state it is in, it is still the M249 platform. However, in use you would have to define its state, in this case "mounted". Perhaps that's just the Aussie military buff coming out in me, but that's what we call the systems. They're mounted in that way all the time on our Bushmasters. So we call them a mounted weapons system, with mounted referrring only to its state. Otherwise, the best description would be "interchangalbe state" weapons systems.

However, in the case of the Mk.II HA/LA DP 4in naval gun, its known as a shipborne weapon, because it's not used in any other state as a designed-in feature. Just saying.

So technically, Essex is right in his judgement. The system may be the same, but its state is what defines its designation.