I have been struggling with Panthera shooting slow on first shot( 20-40 fps slower), and only after sitting 5 minutes or so. Also shooting slow when cold. Someone suggested putting big power wheel on 4 and small adjustment on 4, then adjusting regulator to your desired fps or 10 over at most! It will sound like crap and use lots of air but all is good. Then turn small hammer spring adjustment wheel to where your gun sounds back to normal. You will see the small wheel going from 4 to 3 ( guestimate) and ft per second staying about the same, you want to keep going until ft/second barely lower ( within your desired ft/sec ). Accuracy will return and after 2 days sitting my gun shot a duplicate number over chrono and is much more consistent. I am shooting 500mm in .177 around 900 ft/sec with JSB 10.34 but should work the same with any pellet or caliber. To much reg pressure and not enough hammer spring results in poor results on first few shots, but also to much hammer will result in low shot count and bad accuracy. Find the balance! Happy tuning and I hope it works for you.