The AoA Crosman Hammer Debounce Device is a popular mod' for 22xx and Discovery style guns, due to it's ability to reduce noise and improve shot count by 30 - 50%, while lasting many 1000s of shots (actually its service life is essentially unlimited) in stock or lightly modified guns. However, we've recently learned that in guns equipped with aftermarket mod's that significantly increase hammer stroke length and energy (e.g., heavier and shimmed hammer springs, shortened valve stems, lightened valve springs, etc.), especially when fired with a partial charge or no charge at all, there's sometimes a tendency for the hammer pin to collide violently with the end of the bolt.
Because the "hook" of the HDD - where it fits over the hammer pin - is trapped between the pin and bolt and so squeezed between bolt and pin when collision occurs, prolonged operation in this stressful condition can fatigue and break the HDD in this area, resulting in premature failure and an unhappy customer.
Here's a quick, easy, and unobtrusive mod' to the bolt that eliminates the problem - a small "neck" turned on the end of the bolt to reach inside the HDD and push directly on the pin. This spares the HDD the stress of impact and prevents failure.