I went to a skirm sunday (-2°C) and i only shot with gbb, a hi-capa 4.3 and a g&p woc m4a1 with ratech kit, they shot like they suppose to do :-).
When we took a break i put the magazines in my trouser pockets, that's the trick :-D.
I had a lot of fun, but that is my opinoin, i like realism and i'm willing to sacrifice a little heat(?) by putting the mags in my pants.
The hi-capa was shooting 275 fps and the m4 was doing 330 fps :-).
Grtz Michaël