I am running a #20 in my C-BOB, but, I have others spring weights available and on hand.
I watch the ejection of the rounds. If the empties land at my feet, then recoil spring is too heavy. If empties land in the next county, then the recoil spring is too light.
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Life Member NRA
Life Member NAHC
Former President of the ECPT (Eifel Combat Pistol Team)