I picked up my GSSF Glock 17 Gen4 today (best deal around, but that's another story). Comparing it with my earlier G17 Gen4, it looks like they changed the recoil spring. My new G17 has a prefix of PPN and the spent casing was collected on 6/16/10. My earlier G17 has a prefix of PFE and the spent casing was collected on 2/5/10. I left the pictures extra big so you can click on them to see the detail. The spring is marked "02" on the rear: Here is a comparison of my "old" G17Gen4 spring with the "02" version. Observing the outer spring, the old version is just shy of 20 turns and the "02" version is just shy of 18 turns. Too hard to see what the inner spring differences are (if any). The slide on my new G17 is noticeably easier to draw back.