My 4.25 is running great. I chose to run the 14lb spring since my slide was slow out of the box after cleaning and lots of racking.
With just 1 issue, a stove pipe in the first 500 rounds and my slide really feeling great I dropped in the stock spring yesterday at the range and it ran through the 200 rounds I had left without a hitch and was dropping with enough slide velocity.
I did increase my extractor tension because I had some erratic ejection after the swap, probably due to the higher slide velocity.
It literally takes a few minutes to pull the extractor and give it a few light bends. Now it is throwing the cases within inches of each other.
Very crisp but still too heavy trigger is my only legit concern at this point. I will work on that a bit next. My sight plate came loose again. The locktite I used was pretty old so will pick up a fresh tube and look up the torque specs.
Here are the first shots with the 12lb spring and before the extractor adjustment.
Hammer hit the nail on the head.