The discussion on this has been interesting and made me curious to do a bit more research. In addition, further followup with Bill Kalush revealed additional details on the exact setup of the Catch of which I was previously unaware. I'm no "ballistician," but my experience and research made a few things obvious.
As I mentioned, there's no bullet I'd be willing to stand in front of without fear of grave injury, including a .22 round with a modified load or round. The .22 is used as a match round because of the fact that it is notorious for its' straight trajectory at short range. Once you start approaching 100 meters or more, you begin to see a signifiant drop . To be specific, the typical .22 round has a 69 mm rise at 50 yards . This increases to and 270 mm (approx 11 Inches) at 150 yards which is considered to be the maximum effective range for the round.
Why is that important? Well, if you begin fooling around with the load or round itself, you begin to enter an area in which it is virtually impossible to predict the results for each round in that they'll be almost as unique as a fingerprint. Factory produced rounds share common characteristics while hand loads exhibit common variances.
The one thing you want when you've sighted a rifle on a target that you're holding in your mouth is for it to shoot straight. Tamper with the round, and it might not.
According to Bill, what was used in the stunt was "right off the shelf from WalMart."
In addition, the "sandbagged tripod" was actually an "old pair of camera tripods which in no way could have been set up and been safe enough to just have David take his mark and fire. If we had set this up on a bench and locked it in it still would be extremely challenging to get David into the exactly right position."
Like I said... I'm glad it wasn't me standing there in David's place.
As far as someone volunteering to pull the trigger on a performer staging this type of true bullet catch, I wouldn't. More people are said to have been killed by a .22 than any other caliber.
I think this stunt was generally overlooked in the special, which is a shame given the risk involved in what was an truly death defying spectacle.