So now I've had a chance to check out how the Aguila mini shells function in my 590A1. I installed the Opsol adapter. Takes about 5 seconds. Then loaded up the mag tube. Amazing. I have the 18.5" barrel with an S&J +2 extension. Holds 7 of the 2¾" shells or 11 of the mini shells, plus one in the chamber.
Before heading to the range, I ran two full tubes through the shotgun. I racked slow, I racked fast, pointed up, pointed down, and to the sides. Not a single blip. Every shell loaded and ejected perfectly.
At the range, I loaded 11+1 and fired them all rapidly. No problems. I finished off the box of 20, popped out the adapter in a couple of seconds and loaded and fired some Fiocchi 00 low recoil buckshot.
The recoil from the Aguila mini shells was very minimal. Slightly more than a .223. Maybe more like a .243.
Pretty decent pattern at 10 yards. 9 of the 11 pellets landed within the 8"x10" orange peel target. At 15 yards, it was starting to get pretty spread out, with all the pellets impacting within about 18 inches.
In conclusion, I have to say I like these little shells. They are very pleasant to shoot. Ordered 60 more from Ammo Freedom. I think they would be very good for indoor home defense.
As far as the two adapters...I haven't tried the one featured in the video above yet. The Opsol adapter is much less obtrusive. It fits completely into the loading chamber and is barely noticeable. The other one clips to the outside of the receiver and seems susceptible to being accidentally dislodged. With either adapter in place, You can't mix the mini shells with the longer 2¾" shells. The adapter will prevent the longer shells from chambering.
Here's how it looks installed.