For the arm chair experts i would recommend downloading FM 3-22.68,and read up on what to do with a runaway.
Gosh...what for? Nobody said a runaway wasn't possible, but a cook-off it isn't.
And for those who may be wondering...a cook-off usually occurs when you have a round stuck in the chamber, for example a "failure to fire". If the chamber is "hot", you may get a cook-off.
Can't speak to the likelihood of this happening with the M240 as I never worked on or taught that weapon but I would assume those procedures are still part of the training program.
IMO, there is much more to running a gun than just being able to shoot it, understanding the cycle of operation, immediate/remedial action procedures, operator maintenance, INSPECTION and FUNCTION CHECK should ALL be known and applied.