I was thinking of expanding my current marine army to encompass the entire fifth company. My problem is in trying to understand the numbers of each. There is the command section (Standard bearer, Iron Father, Iron Captain and an Apocathery) then six tactical squads, two assault, two devestator and support vehicles.

This, assuming that the squads are at full strength, that totals over the 100. I understand that assault squad members can walk off and man land speeders or bikes, but do the crew of the other vehicles detract from tactical or devestator squads ? How many rhinos would a chapter as a whole have access to or is it variable ?

Do each of the tactical squads in the company have heavy weapons, or does the number of heavy weapons detract from the dev numbers ?