[Loaded 9mm rounds failing case gauge months later]

When I go to a tournament I keep my ammo in a small cooler, to maintain ambient temperature.

[new acme coated 125 grn fp 38 special no crimp groove better or not]

I assume you're using for 38/357. Likely Acme wanted one bullet for 38/9mm to speed production, 9mm uses a taper crimp. Suggest using either a Lee or Redding taper crimp die after seating the bullet. Note do not over crimp.

[Decapping issues - 9mm with Lee Universal Decapping Die]

Likely some had crimped in primers. If that is the reason new primers will not load until the crimp is removed. Mostly I use a Hornady primer pocket tool and touch up with and RCBS case mouth tool.

https://www.midwayusa.com/product/1012744621?pid=501588

 

https://www.midwayusa.com/product/101293302?pid=465641

[Winchester 9 mm recall]

Has anyone heard back from Winchester on redeeming their recalled 9 mm ammunition?

[Copper rings left in chamber, failure to return to battery]

From the photo cou could it be that your reloaded brass is slightly short and your load is forcing some of the plating into the chamber upon firing. Could be from fast powder causing fast set back of the slide/shell or light recoil spring. The fact that Winchester white box functions kind of says the gun fits some standard.