I have a few boxes of the Underwood. I tried it out in my Springfield TRP, but not something I'd recommend in a 1911. They didn't feed reliably and the coating scrubbed off on the feed ramp which aggravated the feeding problem. So I've relegated it to my Ruger LC Carbine. Runs fine there, but it's pretty stout so not something suitable for a steady diet.
Thanks, it is the full sized 5" steel frame SR-1911. I'll check the spring rate again & make sure I'm right before trying. In all honesty, I've had this pistol since back around '12 or '13 but it hasn't been shot a lot as I don't usually carry it. I tend to shoot whatever I'm likely to carry more.I have found the Wilson Combat spring caddy to be a valuable addition to my 1911 maintenance bag. YMMV.
SPRING CADDY https://share.google/o5ay6LfgLPcthLJvX
Monitoring the distance your ejected brass flies can aid in determining if your recoil spring matches the load, is to strong for the load, or is to weak for the load.
Each variant of the SR-1911 comes equipped with a different weight recoil spring. When in doubt, change the spring with a new spring of known # weight. Springs will loose tension as round counts increase. If an 18# spring is recommended for the load, start with a new spring known to be 18#. JMHO YMMV.