How do you remove the gun barrel and take the BB unit apart on a HL tank and upgrade the power? Getting into the turret is easy but my gun mantlet appeared to be stuck onto the BB unit and wouldn't move after removing the two screws either side of the breech on my Tiger 1. Should it come free with a bit of "persuasion" or is it likely to have been glued there? My BB no longer works properly after installing the barrel extension and I suspect the inner barrel is not lined up correctly with the o-ring on the BB unit.