In my earlier post I wrote that "...I still think that another forty years of development could have resulted in a very useful infantry support weapon."
What I had in mind was something like the pompom but a lot lighter; not a wheeled artillery piece but something more transportable like a heavy belt-fed machine gun that could lob explosive shells over a distance of, let's say 1000 yards at 60 rounds per minute. Something like this:
OK, it turns out that it took a bit longer than forty years, and it wasn't until the war in Vietnam that the US military saw value in a portable short range automatic weapon that could provide high-volume suppressive fire support. This resulted in the "Mk. 19 40mm Machine Gun", developed by Saco Industries in 1966. (Later termed "grenade machine gun" or "automatic grenade launcher")
Still in use today, the Mk.19 (MOD 3) has an effective range of 1 600 metres and a sustained rate of fire of 40 rounds per minute which is not too different to the old pompom of a hundred years ago, but with a much lower muzzle velocity. Also it's a whole lot lighter (33 kilos, gun only) than the pompom (186 kilos, gun only) but still requires a small team of men to operate it when not fitted to a vehicle or helicopter.
Automatic grenade launchers such as the Mk.19 are considered indispensible as infantry support weapons these days and just about every army uses them. The Mk.19 of which more than 35 000 units have been manufactured, is in service with the armed forces of more than 20 other nations. Production and further development of this weapon type and its ammunition is ongoing in the US and a number of other countries, including Russia, China, South Korea, Spain, Germany and South Africa.
Perhaps the Nordenfelt Maxim 1-pounder pompom was just way ahead of its time.