The lightest loads that will function in a Glock 22 is a function of many variables; slide and barrel mass, hand mass, forearm mass, hand compliance, friction, recoil spring force, etc.
The ones you have control over are the recoil spring and the friction. Put a wimpy recoil spring and some oil in the slide to frame junction, and the threshold of the lightest load will go down.
There is a range of loads that work sometimes.
I was testing this week for the threshold of jams in a 1911, and the range from 5.9 to 6.0 gr would jam half the time, and half the time it would not jam. So there needs to be some safety margin from the threshold.