I got a Hobby Boss Leopard 2 recently and would like to spruce up the loader's MG3 a bit--the kit provided weapon is pretty basic. Would it be possible to use an aftermarket MG42 barrel to do this? I know the MG3 is basically a slightly updated and re-chambered MG42, but are there any significant external differences in the barrel that I would need to take into account? Thanks!

Apart from the sights, which at that scale are almost a non -issue, they'll look the same.

If it is a Bundeswehr LEO, you must remember the AA sight in front of
the rear sight : http://images.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/5/55/MG3_Training.JPEG&imgrefurl=http://commons.wikimedia.org/wiki/File:MG3_Training.JPEG&usg=__tzV8zmZiJzWX9pxBSG9AJeIQG7k=&h=768&w=1498&sz=406&hl=da&start=11&um=1&tbnid=ic5BP_sydSlH6M:&tbnh=77&tbnw=150&prev=/images%3Fq%3Dmg%2B3%26um%3D1%26hl%3Dda%26rls%3Dcom.microsoft:en-US%26sa%3DN

Thanks guys!