...saw our hero on another thread ("Accident Advice") providing advice on pistol shooting with a hand injury about an hour ago, so seems he's merely flounced from here?
"You didn't describe the actual injury, but I suffered something similar at the end of 1989. It meant that my ability to pull in my left thumb to my index finger was severely degraded (I'm left-handed). I've no problem bringing my thumb up into the "OK" position, since the muscles responsible for that are in the forearm, it's just gripping things between finger and thumb I have trouble with. After a while, you learn to live with it and grip things with your index and middle fingers. Or if you have to, say, retrieve your credit-card from a machine, you can use the knuckles of the same fingers.
What I didn't notice was any inability to shoot, either with a pistol or with a rifle. The three fingers on your hand (not counting your index finger) have more than enough strength to hold a pistol-grip firmly and, if you try it out, you'll find that you don't actually need your thumb to do it, so I don't quite understand how your weapon-handling ability could be adversely affected."
Funny how despite leaving the army '73 or '72, he's still using pistols and rifles after having injured his thumb in '89.
Props to @stacker1 for Calling out his billy bollocks.