BT 100 Locking bolt wear is caused by a degraded top lever spring not keeping the action securely in battery. The imperceptible movement of the locking bolt when the shotgun is fired with a worn top lever spring wears on the locking bolt and barrel engaging surfaces with each round fired. Our chrome silicon Top Lever Spring is increased in power 15% and will eliminate problems with breaching and locking bolt wear. The hammer spring included in this kit will decrease lock time and make your trigger feel snappy again. An old music wire hammer spring can increase lock time by 50% or more, robbing you of targets. Like our top lever spring, our hammer spring is increased in power 15% and made from high grade chrome silicon wire. It is heat treated and preset for a long life. If you have not replaced these springs, you owe it to yourself to get your BT-100 functioning properly and this kit does it. We also include a new firing pin and firing pin return spring so you can change out all the coil springs and your firing pin at once. J&P Custom Products, LLC | Gun Springs Manufacturing