USA models more fps

[ozzy]

Just wondering whats the difference in the 2 models between Canadian and american models of the same co2 air rifles? For instance the crosman Night Stalker. Canadian version is 495 fps and American is 580 fps. Is it a valve or what?
I know our law states it must be under 500 fps with out a pal.

 

[nabiul]

On their pneumatic rifles, crosman acutally drilled a bleed hole in the path that supplies air to the barrel to lower the pressure when fired. For the co2, it's probably using a stiffer spring which closes the valve faster or maybe a smaller transfer port, restricting the speed of gas escaping.