longspurr,
That's an intereting idea. One measure of recoil - Free Recoil Energy (FRE) - is proportional to the (m*v)^2, if I remember correctly. Based on similar reasoning, I believe that for a given pistol & spring combination, there will be a minimum power factor (PF, again m*v) floor to achieve proper operation, including locking the slide back.
For my CZ-75B-SA, I computed this floor to be around 90 PF. Much below that and it would short-stroke or not lock the slide back properly.
Though I have not tested it yet, I think that this PF "operation" floor should be the same even when using different bullet masses. For example, a 115gr @ 870 has 100PF, but a 124gr need only go 806 fps to hit 100 PF. Similarly, a 90gr would have to go 1111 fps for 100 PF.
These 90gr Gold Dots don't penetrate and expand very well even at their
design velocity out of a .380 Auto. I think the bare gel penetration was 9.3" with expansion to 0.59" at 934fps. (
Link to FBI data ).
For my low-power practice loads, for people who don't like recoil, I use a 115gr PRN (lead, copper plated round nose) West-Coast bullet with 3.4gr VV-N320 or 3.2gr Bullseye, seated to 1.100 - 1.120" (doesn't matter too much at the low loading), with "any" brass. This goes about 900fps and doesn't recoil much more than .22LR, in a full-size gun. It is not strong enough to cycle a BHP or Glock, however.
-z