The Spring Pack allows fine tuning of the JP Silent Captured Spring System. Comes with 5 different springs of varying strength. So if your gun is cycling too soft and not locking back on the last round with your JPSCS, you can try a lighter spring. If your gun is running too hard and bottoming out, you can try a heavier spring. This allows you to fine tune the cycling of your rifle while using the JPSCS system.

These springs are only compatible with the JP Silent Captured Spring System. They do not replace standard buffer springs.