As Gee Tee has said he built me a Pumpmag, which is up for sale by the way ;-) I shot a Cocker pump before, which was a lot heavier and the pump action was a lot longer. This made it a bit slower and less consistent shot on shot. Now that may have been down to lack of practice but the pumpmag has got a much shorter pump stroke. I didn't have slam fire on the Cocker I owned, which may have evened it up.
Rich