Works with factory steel or new synthetic guides. Works well with all Hw77's from 1982 on up.

For a basic hunter-plinker, just order a piston seal and this spring with tar and your set. Please check lockup of newer 77-97's and space breech seal as needed. On these guns if you use the factory breech seal you should replace it often. If you do not the gun will lose power and you create other issues. It's just business as usual with the newer guns.

Production varies from 36-37 coils on runs.