In what way is your Luger cycling improperly?
The recoil springs can age, and if one was replaced with the incorrect spring at some point, it might be shifting the "sweet spot" of the action's cycling.
Also, look closely into how you grip and support the gun while firing it. This can have more impact than the recoil spring.
If you are near Raleigh, let me know and we could meet at an area gun club to check things out.
There is a
kit of recoil springs available from Wolff, but as Don says it may only complicate things to start swapping them.
in fact, if you look at our
FAQ PDF, you will see that there is a wide range of recoil springs that were used in Lugers. The cycling action is balanced and dependent upon several things including the length of barrel, the speed of the powder burning, the weight of the bullet, cleanliness and lubrication, the recoil spring, your hold control and support.