This weekend I had a chance to try two things out, first, I'd re-stocked my Mossberg 500 with the ATI pistolgrip buttstock. Looks pretty good and worked really well, to boot.
Secondly, and even better, I got to try the Aguila Mini slugs i'd bought at the Reno show.
That's a 2 3/4" #2 buckshot shell in the middle. The mini's are 1.25" tall, and have a .9 oz. lead slug.
The target for this testing was an old mailbox (you know, the square R2D2 looking ones?). We moved it out, stepped back 20yds, and I pulled the trigger. A nice 1" wide hole was in the front panel, and a 1/2" deep dent was in the back. We heard the slug bounce off the bottom after I shot, it was kind of funny. You can fit 8 of them in a five shot tube, too.
A few more shots with the same target yeilded similar results. Someone then took a couple 50 yd. shots at a paper target. Accuracy was acceptable, although the shotgun with a single bead sight (talk about kentucky windage) might be part of the problem.
The only problem with the shells is that the lifter arm on the mossberg doesn't have a long enough middle leg to stop the shells from tilting out the bottom when you pump the action slowly (man that sounds perverted). The simplest fix would be to weld a small piece of metal onto the middle part of the lifter arm. If you pump it quickly, the shells feed no problem, however, not everyone will always rack the slide that fast.
At $6/box of 20, these are fun to be had for a reasonable price. I didn't get any of the buckshot ones, but they are also available.