The following was posted by Boogaloo, a Senior Moderator, in another forum. The content, which was borrowed from another message chain, is good enough to warrant a place in the FAQ area, too. Boogaloo tells me that forum member DLEONG originally posted it, so credit for the original work goes to him. My thanks to both of them.
Quote:
Most CZ40B owners use either the 18, 20, or 22# CZ75B recoil spring from Wolff, although as Walt said, they have to be cut down to work in the CZ40B.
The following procedure addresses the particulars of fitting one of these springs to a CZ40B. Apologies to the original author who provided this info since I don't remember who it was -
Just a quick note: merely ensuring that the slide locks back on an empty magazine does not necessarily mean you have cut enough coils off the recoil spring.
At full recoil, the rear of the slide's recoil spring housing hits the stop surface at the front of the frame's locking block. This is what limits the slide's rearward travel.
On the 40B, there is about an additional 1/8" of slide travel between the point where the slide stop engages, and where the spring housing hits the frame's stop surface. If you cut off only enough coils to ensure the slide locks back on an empty magazine, the spring might still compress fully before the slide hits the stop surface. If this happens, the spring essentially becomes a solid tube and absorbs the full brunt of the recoil shock. The spring will be destroyed in a matter of a few rounds.
To ensure the slide is able to retract fully with a new, modified recoil spring, I would do the following:
1. Field-strip the pistol; remove the recoil spring, rod and barrel.
2. Reattach the barrel-less slide to the frame and retract it fully. Use a pencil to scribe a line across the slide/frame seam line.
3. Remove and reassemble the pistol, using the new recoil spring, and begin cutting off coils from the spring until the scribe marks line up. At this point, remove an additional quarter of a coil to account for heat expansion of the spring during live-firing.
My 40Bs have cut-down 22 lb. Wolff springs intended for the 75, and both function flawlessly
