If one were so inclined to MAKE the G36 work as a 10mm you would need to have the breechface welded and re-cut to 10mm dimensions. Furthermore, I believe (but I'm not sure) that the G36 barrel will only fit a G36, so reverse logic would dictate that the G29 10mm barrel would not fit the G36 slide. If it will then redoing the 36 as a 10mm wouldn't be too hard. However, a barrel would be expensive if you can't just use a G29 barrel. Hope that makes sense.