Made it to the square range yesterday. As an ammo experiment, I had bought a box of 50 Winchester "Ready" Flat Nose 230 FMJ 880 fps (sku RED45) and 50 S&B 230 JHP 889 fps (sku SB45C). Gun still has the 18.5# WC recoil spring and factory 23# mainspring. Other non-factory parts include a WC BP ambi safety, WC flat bottom FPS and a WC extra power firing pin spring.
The Winchester ammo had 3 fail to chamber malfunctions during fire. The bullets just didn't go in. I also had 2 malfunctions, where it would not feed when being loaded (sling shot). This was with my CM RPM 8 rounders. This ammo is also very dirty and very smoky. Not going to order any of that again, that's for sure. The S&B hollow point had no issues, all 50 rounds went down range with no drama.
No problems with the 18.5# spring. I didn't do much in the way of metrics, but I played some with top of front sight hold versus combat hold. I did have two instances of locking up the slide stop, where I inadvertently push on the pin, and lock up the slide. Argh.
I'm happy with the 18.5# recoil + 23# mainspring combo, at least as much as I can be, with the very small number of rounds through the gun, and based on my very limited 1911 experience. I don't perceive any real ill effects on my shooting; I shoot about as well / poorly as I did previous to the spring change.
Overall, it was a good day, even though neither ammo worked out. And I learned the gun shoots to combat hold, with the FO front, which I prefer for irons, so that was a useful discovery. I still have trouble seeing the front sights, my arms aren't long enough these days. Gun is at 448 rounds.
I plan to standardize on Federal American Eagle 230 ball, and keep the S&B SB45A ball as backup, since the gun is cycling 100% with that ammo.