I have a set of the exact same magazines, they feed very well...provided you don't overload them.
While some may be having issues using the smaller diameter Madbull BB's, I have not. In addition, I have had similar jams while using Bastards, because I overloaded the mag.
If you're feeding with a standard loader, as soon as you start to feel the BB's requiring more force to insert, STOP. Yes, the smaller diameter of the Madbulls may make them more prone to jamming, but it has more to do with the fact that the magazine is plastic.
If you overload them (force the spring compression) the mag will begin to split slightly, allowing for the BB's to start lining up beside one another instead of on top. Be mindful of how you load these, or any other plastic mags and you should see reduced instances of jamming. A little silicone oil (as suggested earlier) will help as well.
Last edited by Scopedog; January 14th, 2010 at 19:28..