So what of this other gun?
The gun is in Meppen, Germany. It's a research gun (like VERA) intended for fuze testing (like VERA). It's concept of operation is your standard hybrid gun with burst disk (like VERA). Unlike VERA, however, it uses methane/air instead of propane/air.
The layout is pretty interesting. The gun consists of two rail cars on a short piece of track. One (reasonably short) car holds the combustion chamber (with about 20 methane K bottles stacked on top). The other car holds the barrel. To load the gun you unbolt the breech, separate the cars, and crane in your projectile. The recoil mechanism is to simply let the gun roll backwards a few feet on the railroad track.
Conceptually, it's a very simple gun. The scale is enormous. Actually, it's not THAT much bigger than VERA if you just look at length of barrel and such. But it's obviously made of much heavier stock. I don't know what the mix capabilities of the gun are but they're obviously pretty high. How high? I just don't know.... But it shoots BLU-109s to trans-sonic velocities.
Still looking for more information.
On another note: I also got to tour an AC-130 last week. That was pretty cool too.
