New FAC. power kit for both older and the later high velocity guns. Can be used in any HW77-97-60-61.
Two spring guides and spring. Supplied with black tar.
If your getting high 700's or very low 800's in a new gun in .177 and sub 700 fps with lwt pellets in .20- Than your new gun has issues that higher power kits will not fix. Putting in a higher power kit will not get more power and often lower power. Sealing and barrel issues are the cause. With guns after say 1999 more spring gives less power unless you fix the compression tube issues. Flat spots, out of round, and often the end of the comp tube is leaking and not sealed. When these things are addressed then the power comes back. If not corrected you will destroy all the seals and springs in short order because you are essentially dry firing the gun every shot. No a flex hone and polishing does not fix leak down issues or out of round tubes. And yes this is the issue with your gun.