The RPG-40 was on display at MSPO 2008. The Centre for Research and Development Equipment Mechanics (OBR SM) and Military Technical Academy, which I assume are Polish organizations, have developed the RPG-40. Despite its name it has nothing to do with the Russian RPG-* arms and does not fire rocket propelled grenades, just the standard 40mm variety.

The RPG-40

It holds 6 rounds and features an oversized chamber so a variety of lethal and non-lethal ammunition can be chambered – limited by how much pressure the weapon can withstand.

Oversized 40mm chamber

It may be in direct competition with the South African Milkor MGL (M32) that is currently used by the Marines in Iraq. It looks like it has a very similar spring-loaded magazine, which rotates after a shot has fired. I would not be surprised if the MGL technology has been licensed.

Marine with M32 MGL (MGL-140) in Iraq.
Photo from Wikipedia

MGL MGL Mk-1

The MGL is a scaled up version of the Striker/Streetsweeper/Protecta rotary magazine 12 gauge shotgun:

Striker shotgun with 12″ barrel. Photo from guns.ru

More info here (translated in google)

I have done my best to find accurate information about this firearm on the Polish MSPO 2008 website. I do not speak or read Polish so I had to rely on Google Translate. If I got something wrong, please correct me in the comments.