When I lived in Kansas, a friend had one of those mini revolvers with both .22 and .22 mag. cylinders. When we chronographed them, there was only 5 foot lbs. difference between the .22 mag and the short. You should have chronographed a round designed for short barrel pistols such as the Hornady Critical Defense in .22 WMR.
As you know, the .22 Magnum's real name is .22 WMR, which stands for Winchester Magnum Rifle. The problem with most .22 WMR loads is that the powder is designed for a longer burn in a rifle length barrel, so the performance in a shorter barrel handgun is, shall we say less than optimal?
But the Hornady Critical Defense load has two advantages: First it has the Hornady FTX jacketed hollow point bullet that is designed for self defense, and it is loaded with a low flash pistol powder designed to burn better in handgun use.
https://www.hornady.com/ammunition/rimfire/22-wmr-45-gr-ftx-critical-defense#!/
“...the .22 Magnum’s real name is .22 WMR, which stands for Winchester Magnum Rifle...most .22 WMR loads...the powder is designed for a longer burn in a rifle length barrel...performance in a shorter barrel handgun is...less than optimal...” [Yo-Yo, post 35]
The R in WMR stands for rimfire, according to period literature from Winchester. A minor point of nomenclature; scarcely anybody today calls it anything except “22 Mag.” Everything else you posted is dead on.
Rimfire rounds pose problems in autoloaders, handguns, and especially in small concealable handguns for self defense.
I spent 13 years working part time for a small family-owned dealership, in gun repair. One of our most common modification requests was for trigger pull “improvement” (read: reduction) on rimfire handguns. Many women found rimfire double action pull weights impossibly heavy. We worked on the problems at length; our boss was female and was careful to attend to the concerns of women as customers (in contrast with numerous other dealerships in the area, many of which had trouble emerging from the prior era, when guns were more of a manly thing, territory the “little lady” did not venture into often).
We had to disappoint most customers: as other posters have pointed out, rimfire rounds always require a heavier blow to ignite reliably. The moment we lightened the pull, on just about any handgun, failures to fire cropped up. It was always worse with very small handguns, which had smaller, lighter hammers with a shorter throw, and thus required a much heavier mainspring. 12 to 15 pounds double action was lighter than average, when we measured pull weight on rimfire handguns.
22 WMR was designed for bolt action rifles. Autoloaders chambered for it - rifle or handgun - always experienced feed reliability problems, quite apart from ignition reliability. The rimmed case was simply too long and narrow, and so thin it often sustained damage while feeding. We never could induce a 22 Magnum autoloading pistol to function all the time; strings of 25 to 30 rounds would feed and eject OK, then the arm would misfeed. Kel-Tec’s PMR-30 seems promising, but I’ve not seen one yet, nor tested any. Field testing may tell.
All rimfire handguns are very sensitive when it comes to ammunition. Applies across brands and can sometimes appear from lot to lot of a nominally identical loading: rounds made several years ago may work, but rounds that just arrived from the factory will not. Someone determined to use a 22 rimfire for self-defense would be prudent to buy a number of different brands and loads, then test them extensively for accuracy and feed reliability, and ignition reliability. Accuracy and reliability seem to be independent variables: often, we found that the brand & load delivering best reliability exhibited poor accuracy, or the most accurate load was less reliable.
Compromises cannot be avoided.