I have had a recent fairly serious hand injury, then elbow surgery for a torn and detached tendon in June, and these events have changed my shooting pretty drastically for the worse. I have hunted upland birds for years, and have always been a pretty good shooter, somewhere in the 90% range pretty consistently over the years (67 now.) In November of 2006 I caught my hand in a bandsaw and severed the flexor tendons to the little and ring fingers of my right hand. I am right handed. The surgery that followed rejoined the tendons, but the hand will not close up completely anymore at the right side of the hand where those two fingers are. The elbow surgery required drilling three holes in the bone to reattach the tendon, and there was a fairly routine rejoining of the severed portion of the tendon as well. This was caused by using those little hand-held clay target throwers, I am sure you have all seen and/or used them. It caused a basic hyper extension of the elbow with pretty serious damage. I don't recommend you use them anymore.
The bottom line is that even after several months of rehab therapy to regain strength in the hand and elbow, both are weaker than they formerly were, and both are now changed in the way they move and operate.
I just got back yesterday from a nice hunt at Heartland Lodge, complete with 10" of snow on the ground. The dogs were able to find plenty of pheasant hunkered down under sheltering blow-downs and/or bent over milo, so we had good success in general. I found my guns that I have been using for several years now smacking my second finger just as described above, where they never did that before. I am inclined to agree that it's caused by a too loose grip on the gun. When I had full strength in my hand and arm, (the elbow surgery changed the forearm strength as well) I had no problem, now with reduced strength I do get smacked.
I'll continue to try and regain strength with the therapy routines they gave me to do, but I plan on installing the rubber thingamabobs on the trigger guards of my favorite guns. It's very unpleasant after six or eight smacks in a row, particularly in 20 degree weather. My length of pull requirement has not changed, so I am pretty sure it's a loose grip that is the main culprit.
