Yes, but it's only muzzle loading barrels that are tested by being laid on the sand bed and fired by a black powder trail. For breach loaders the proof house makes their own proof load cartridges to test barrels.
The Birmingham Proof House does guided tours for pre-parties, check their web site for details. Their gun and cartridge museums are worth seeing.
The place still looks same as in that 1951 film, in fact for facilities for testing breach loaders it hasn't changed much since the 18th century except it was in open countryside when it was built. They can't test fire cannons from the front door like used to do anymore they would now hit the railway viaduct.