Did you put back together the rotation thing on the back of the turret right? Look in one of the threads for the dtg mods and look at the internal pics and see if you got it right. Also are your barrels straight? I had that problem with my dtg the barrels were so unstraight they were rubbing against the walls of the gun causing to much friction for it to rotate. If that is the problem you could either sand down your barrels or completly redo the mod. Hope this helped.
How do you know you have to live in the Uk to order one of these?
Well you do not have to live in the Uk but Shipping to the U.S. would be a real pain for me. But yeah if someone could convert that to shoot stefans it looks like you could have a very reliable five shot pump action gun.