Use less coffee...
Muz
Believe me, I tried a lot of things to get good tasting coffee out of that Moka, causing an explosion was just one (accidentally of course). Most of the pressure is built up from the small holes in the screen. I am pretty sure that the water can defuse faster through the grounds than the through the holes. So I believe sure you keep the gounds compressed to avoid residue on the machine which eventually molds. Of course, its not like I solved some PDE's here, so this is all hand waving.