From the wikipedia page, it appears they initially used physical contacts to send electrical pulses to the primers, but they now use induction coils around the barrel (contactless) to send the firing pulse to the primer.

The induction system would be the most reliable, but would also be the least energy efficient, i.e. I doubt that piezoelectrics would be able to provide enough energy to inductively fire a primer. That said, I dont know how the primer works, so I could be completely wrong.

Still, a hand cranked dynamo on the weapon should be able to charge it up enough for a fair amount of firing.

This MAUL system would make a great combat shotgun on its own – a pair of them side by side or over-under would give you a short, light, easily reloadable 10-shot semi-auto shotgun with 2 switchable choices of ammo. Hell, you could even go to 3 or even 4 barrels if you wanted more ready-to-go shots. The trick would be keeping the barrels light enough, which for shotguns and their relatively low pressures wouldn’t be too hard.

If the ammo was cheap and simple enough – a plastic cup plus ’special’ primer – you’d have a winner.

Do you know how the system works in the MAUL? Does each primer have a piezoelectric “firing pin” behind it?

There’s a few russian weapons (rockets, i think) that have a small dynamo attached to them for charging before electric firing.

I can picture an ultracapacitor and dynamo next to a battery, and i can picture the loading action (pump, break, whatever) charging the capacitor enough for a few hours standby. If the battery is dead, you always have the dynamo.

I can also imagine using the firing of the weapon to charge the battery – some coil around the barrel and a small magnet in the base of the ammo – and hey presto, you have a gunpowder powered generator. One shot would be enough to power quite a few more afterwards.