Jabalihunter,

I found I good one in the area you wanted (near Paderborn in the NW of Germany): www.jagdkino.de The website is in English also, so that might help. The one in Berlin is not known to me, but probably part of the DEVA shooting complex. The one that ArnoldB mentioned (Belgium) looks good as well.

500 Nitro: I agree. Correct ammunition is the first step, if it fits the gun, then most modern barrels shoot extremely accurate. If not, working on the stock / properly cleaned /maintained barrels will usually do the trick.

With rather slow nitro express calibers the above mentioned is not even a big issue: Slow calibers with heavy bullets are almost immune to variations in powder load and bullet weight. I tested several loads in my .404. Whatever I brewed up with 350 and 400 grain bullets shot at virtually the same point of impact (all groups combined appr. 1 inch at 100 m, only a 280 grain drive band bullet at extreme speed had a different point of impact). So, if the single barrel groups are already small, then a two barrel group can also be very small, especially at the slow .470 speed of 2150 f/s - it simply does not heat up the barrel as quickly as say, a .375 so the first 4 shots should not warp the barrel-bundle too much. Therefore, most bigger groups shot from doubles are probably shooter's error. Looking at the recoil pads that I see on most doubles I am not surprised - you can only shoot a heavy-recoil gun well if it is not painful. Most people would shoot magnums a lot better if they installed a proper pad.