If it helps anyone, back around 2012, when I was hunting recoil springs for my PC 4563 and 4566 45 CQBs, s&w could not tell me which spring they took.

I had to track down their designer, Mr. Paul Liebenberg at his current shop, Pistol Dynamics to find the answer. He told me they used the standard factory spring from a 4006.

I bought a few and they work. Hopefully this helps someone else. Regards 18DAI

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7 +1 Rounds of hope & change