Close Quarter Firefights

[Caradhras]

I am using 1st edition rules T2K - my group are fighting in the Red Star/Lone Star scenario which includes house to house fighting and some other close quarters stuff (wont spoil it for those who may not know the details).

My question is - how have GMs applied rules to show the lack of functionality of larger firearms in close quarters? SMGs and combat shotguns should excel here in infantry actions but the rules dont accomodate.

My gut reaction is a simple skill minus for certain weapons.

-20 CRM bulpup style

-30 CRM battle/assault rifle

-40 CRM anything larger

Ideas guys?