Don't bother with reloading it. Better, VERY carefully engineer the launch tubes to be as minimalist and lightweight as possible for one-time use, and once fired, use it as a doorstop, and hook the sequencing control and possible sighting equipment up to the next preloaded package, just as is done with the disposable tube of a LAW antitank weapon or just as the tracker and firing units of the Stinger MANPADS ground-to-air missile or Dragon antitank missile launcghers are attatched to preloaded launch units. That allows them to be lighter, since they're to be used but once, and if made of non-strategic materials such as advanced plastics/polymers, composites or ceramics, can be easily disposable- and troops in the field will always find uses for the leavings.
Chainfires are an obvious potential problem. One way of overcoming that problem is if every tenth, or fifth, or third *projectile* rather than being the usual slug or shell, is instead filled with a liquid bore cleaner and coolant. In something the size of a 40mm grenade launcher, that might not be a problem, with only a few rounds per short tube, probably 10-12 or so. But in the fixed multitube units, that might be more of a concern, just as it was during the Civil War when improper operator input resulted in *stacks* of bullets and powder charges in the rifles of that day as scared troops forgot to discharge their weapons while repeatedly reloading- and then would touch one off, sometimes with lethal results on both ends.
-archy-/-