That's a nice way to burn the flesh off your finger there with a revolver. I've seen that injury more than once. It's not pretty. Ruby must have had the 1st finger down on the frame or he would have gotten it toasted a little bit. The bird finger is the longest, heaviest and strongest finger for sure, and not surprised someone would use it. But it's also equally strong at reenforcing your grip.

Here's my issue with the middle as a trigger finger, when I hold any gun this way I'm forced to put the middle bird finger into the trigger guard to get a stable grip. If I run the index down the side of the gun and I can't effectively hold my trigger middle finger outside of the trigger guard without feeling like I have a half-assed grip on the gun in general. I can never feel totally safe with this method.

Maybe it's just my hand but this also rides my flesh up higher on the rear of the gun to a point I'm much more likely to loose some flesh with an automatic. I also noted on a website how they illustrate a S&W bodyguard as an ideal gun for this technique but when I use this method the gun is actually so thin profile the index does not actually ride down the right side of the gun naturally, it bends inward then up the side of the gun due to the wider hand compared to the thinner grip. Not all that natural at all...

This is a more detailed reason why I tried but then abandoned the middle trigger finger method. Back to my standard way of using the index finger for the trigger is very natural, safe and works on every gun I own consistently. I mean this respectfully of course, I don't have enough knowledge to comment other than stating what works best for me, but that is why.