As far as
3rd Gens are concerned, either standard production or Performance Center, the 4040PD is the only one with a scandium alloy frame.
Parts unique to the 4040PD, beside the obvious frame, slide & barrel, and the magazine already mentioned, there are a few others:
- the slide stop assembly: the slide stop's follower arm (that engages the magazine's follower to lock the slide on the last round) is shorter than that of a 3913/3914 (.207"-vs-.276").
The shorter slide stop follower arm is so the fatter nose of the .40 bullet will not incidentally bump the slide stop's arm falsely locking the slide back.
- the magazine: the 4040PD mag has a special follower with an extended tab on the follower's left side (to contact the shorter slide stop arm) and a bearing insert on it's right side to keep it pushed to the left.
- the recoil spring guide rod: is a PN# unique to the 4040PD also. It's has a small diameter rod, .236", because it uses the dual/nested spring set, as well as being colored black.
- grips: they are factory Hogue style grips & also are PN# unique to the 4040PD.
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