Welcome, iwizz.
When you build the armory your manpower maintenace burden (MMB) is reduced by .1
IIRC when you build the weapons stores upgrade the MMB is reduced an additional .2
When you produce the Command Squad, it is supposed to reduce the MMB by .1
Each level of vet the Command Squad receives further reduces the MMB by .1
Unfortunately not all of this is working correctly. When you produce the Command Squad your MP rate goes down by about 5/min. even if there are no MMB squads, (ingeneri and conscripts don't count).
The last time I checked when I built the Weapons reserves upgrade my MP rate increased by 6/min.
