The Real Answer
I gave up on the .22 Jet in the Smith & Wesson but I did not give up on the cartridge. The answer was not a sixgun but a single-shot, namely the Thompson/Center Contender. My particular Contender .22 Jet barrel is a 12″ octagon version. I would prefer it to be a Bull Barrel but I certainly cannot fault the way it shoots with carefully selected loads.
My powders of choice are typical for loading the parent .357 Magnum, namely #2400, H110 and IMR4227. For reloading dies I use a two-die RCBS set as no expanding die is needed for this milk bottle-shaped case. There is certainly no lack of choice when it comes to .22 bullets and both Hornady and Speer offer ones in the proper range of 40 to 45 grains. Hornady also offers of choice of diameters, 0.222″ and 0.223″ while all of my Speer bullets are of the 0.224″ variety. All of these work well in the Contender barrel.
With the Hornady 40- or 45-gr. bullets I use either 10.0 grains of #2400 or the same amount of H110 for a slightly lighter load. With #2400 these two bullets give muzzle velocities of just over 2,300 fps and 2,230 fps respectively with groups of 1″ for three shots at 45 yards. This particular Contender barrel really prefers Speer 40- and 45-gr. Spitzer bullets especially over 10.5 grains of #2400. These loads are so accurate I wouldn’t even mention how well they shoot if I did not have a witness.
Better and better
With the Speer 40-gr. Spitzer over 10.5 grains of #2400 the muzzle velocity is just under 2,400 fps, which was the original muzzle velocity for the .22 Hornet in a long rifle barrel, and groups three shots in one-half inch at 45 yards. I thought this would be about as good as it gets, at least with me doing the shooting, actually better than I had any right to expect but would you believe things actually got better?
Switching to the slightly heavier 45-gr. bullet over the same powder charge sees the muzzle velocity go up 50 fps while the group was cut in half — three shots in one-quarter inch! In 40 years of shooting Contenders in everything from .22 Long rifle up to and including the .500 Smith & Wesson Magnum, this is the most accuracy I have ever attained.