[i]My reply is based off of active duty experience only ....[/i]
In the big picture, they probably don't have a need for anymore magazines than that.
All units do [u]not[/u] rate the same type/quantity of equipment. The 101st M4's with RAS, Aimpoints, PAQ-4's, etc. that you're seeing in the news are a perfect example.
You will not see this equipment, even the M4's (in any quantity), in a brigade headquarters signal unit. The Army has deemed that the mission of this unit doesn't support the need for this type of equipment.
Now we're talking about a Reserve unit. Two factors come to my mind as to why they in particular only have two magazines per weapon:
1) The unit's mission doesn't require more than two per - I doubt that the 1/187th of the 101st is being pulled out, and this Reserve unit is taking its place.
Someone in their command structure determined that based off of their mission, they only need two magazines per weapon.
2) If they do rate the basic issue of magazines per weapon (7), the unit supply section hasn't worked the system like it should, along with the higher headquarters S-4 section.
Any unit arriving in an operational area will be issued what they need to accomplish their mission, or be able to acquire it through supply channels.
Supplies unique to that area of operations will be in-country to be given to arriving units, which keeps them from having to hassle with procuring it and bringing it themselves.
My 18 years in the Army makes it unthinkable to me that a unit (even a Reserve unit) would have to go to these means to acquire equipment. Everyone who I work with that I've mentioned this situation to doesn't see a situation like this as plausible either.
Got a bunch of good laughs over it though.
Chris