A cheap fix for your problem would be to drop down to a 15 pound spring. However re-springing the gun will not make you a better reloader. It will just let you use the load you have. I can't give you a good working load with 115 gr because I never use them. You have to push your velocities higher with 115gr bullets to get your slide to fully function. On your next order switch to 124 gr. The 9mm luger was designed around a 124gr bullet. The only advantage of 115gr is they are a tiny bit cheaper. I agree with Richard that WSF is a good powder for 9mm. It is my current favorite for 124gr.