Is the proposition that you've got him an MP5 and you're weighing up having load-carriage with spare mags vs purely 1 drum mag in the gun and no rig of any kind? If so honestly wouldn't recommend the drum. The weight that people notice most is the weight their arms are having to support all day. A very compact rig with some plastic mid-caps for an SMG weighs genuinely naff all and the mags will probably be cheaper, certainly easier to find than a reliable drum, with more chances of working properly and if one doesn't work you just swap mags, whereas you're stuffed if the drum gives out.
