I have two UCLs.
Two boxes of .22s will load ten mags in less than a minute.
You will need to clean it periodicaly cuz the lubricant on the lead will eventualy foul it up. A shot of RemOil and a patch to clean it up works great. There's also a couple adjustments that may be needed to get it to work nice. Screwdriver stuff.
Pawns youtube link makes it look much more difficult than it is.
Once you get it adjusted and cleaned, it will load a mag in about a second.
You're gunna love it.