@Gary_H Not exactly on this topic but applicable since you have shoulder issues is a shooting technique favored by some European SWAT types with their HKMP5’s where the sling is your shoulder stop. Instead of using the butt stock as a “lever” in the shoulder as most American’s are taught to do. They adjust the sling so that they push the gun away from the shoulder and hit the stop(s) on the sling for stability. It takes some time to get the sling set up properly but it does work well when practiced and adjusted.
Cheers,
Craig6