I don't get how adding one LMG adds 3 to the APFP, but combining three LMGs gives an APFP of 18 ...
Dave is combining 3 squads (with 5 firepower each) and giving them one LMG (APFP of 3) to get 18 APFP. In his other instance he still has three squads (one platoon) with each squad carrying an LMG for a total of 24 APFP.
(No, I don't have the game. Just wondering.)
What're you waiting for... it's well worth the money!