Regarding the slide motion I have experienced, after a month of tinkering with both my 40 FS and 40 C, I have made more or less a circle and have gone back to wrist support when shooting offhand as a major contributing factor.

The premature slide lock I had experienced with the compact disappeared after adding tension to the spring.

I shot quite a few rounds off an old plastic Hornady pistol rest over a chronograph, testing both .40 and .357 Sig loads. When pressing the pistol firmly into the rest, NO slide hesitation was felt when firing, regardless of the number of rounds in the mag or load fired.

When firing the same loads offhand, the heaviest loads would start to experience the "hesitation" with 5 or 6 rounds in the mag. When I deliberately left my wrist more "loose", the feeling of hesitation would worsen. Again, as I mentioned in a post above, my wrist strength is not the greatest to begin with.

I also had a moment of enlightenment the other night when unloading some full .40 mags after a cancelled range outing. As I started shucking the rounds out, spring tension was fairly light until there were six rounds left in the mag. The tension at that point actually seemed to increase dramatically. This was repeated in each of the mags, full size and compact that I was unloading, probably a dozen total. It appears that the shape of the mag body contributes to this condition. The five-round point is approx where the mag body starts to funnel down.

The increase in mag tension at that point would increase slide drag. Couple that with a "less than firm" grip and this would reduce slide travel and may account for the slide hesitation felt.

This may also confirm why reducing magazine spring tension by either clipping the springs as reported by some or repeated use results in improved operation.

Please try this for yourself and let me know what you think. Simply load the magazine to capacity. Slide the rounds out one at a time and note the approx force required to slide them out. If you feel a change, note how many rounds were left in the magazine when the change was felt.