I have shot them through my Mossberg 590. The Mossberg pumps are about the only ones that will reliably feed them with the Opsol adapter. They definitely won't cycle a semi auto, but they sometimes will feed in an 870.
Aguila has been making them for several years, but Federal just came out with their 1¾" shorties. Aguila buck shot is loaded with a combo of 7 #4 buck and 4 #1 buck pellets. The Federal shorties are loaded with 15 #4 buckshot.
They both claim muzzle velocities of 1250 - 1300 fps. These mini shells are very soft shooting compared to the 2¾" buckshot shells. Feels more like a 410. I can load 10 of them in my 18½" 590 compared to 6 of the regular shells.
The main draw back, besides not feeding in some models, is their cost. I don't know how a shotgun shell with less of everything would cost double or more than a regular shotgun shell. While the Aguila shells have come down in cost, I've seen them as low as $12.99 per 20 online, the Federal shorties seem to be priced at about 2 bucks a pop. MSRP is around $20 for a box of 10.