Dimreapa's got it spot on. Reloads aren't for a type of weapon, it's for a specific weapon. Two reloads, one for each gun, would do the trick.
When taking shots, the player will have to announce whether it's his first or second shot that has the reload, in case a 1 is rolled. Don't want to roll a 1 then go 'err, which one was it again?'