I have a PC 45 CQB (similar to the 4566) and have the same problem with the trigger spring. In my case the spring has completely broken off.
My 45 CQB has served me as my conceal pistol of choice, despite the weight. I also regularly shoot this gun almost every time I am at the range. This...
I picked up a magazine (2008 Handgun?) at the airport a few months ago. It was the poly shootout between the Glock, Springfield, HK and S&W. The S&W had the superior marks.