Today I fired my HD Shotgun with the Knoxx Butt Stock and Forearm. I also fired a Western Auto copy (Revelation) of a Mossberg 500. Both shotguns were 2 3/4 inch 12 gauge shotguns. I fired each with bird shot, No 6 and No 7 1/2. I also fired the HD shotgun with Winchester 2 3/4 inch double ought 9 pellet buckshot.
There was a noticeable difference in the felt recoil between the HD shotgun with the Knoxx Buttstock and the Western Auto Revelation. In fact the Western Auto Revelation's felt recoil using bird shot felt stronger than the HD shotgun's felt recoil using the double ought buckshot. To be fair, the Western Auto Revelations butt pad is very old and probably has little noticeable effect.
My intent when the project is completed, is to keep the firearm loaded with double ought reduced recoil tactical ammunition as used by many police agencies.
There are more additions on the way, so stay tuned.