There are several factors, but I just discovedred one today. I put a 14lb recoil spring in my SA which is new and only has about 50 rounds through it. The reason I put the heavier recoil spring, is because I have read CZ's are under sprung, and are about 12 lbs. Guess what happened... I got a few shells in the face, and it was not throwing the brass far at all. So I will be going back to the lighter recoil spring.
So you may want to go down a bit on the recoil spring, and it may work!!