Warning:
If using a semi-automatic or pump action shotgun with an "elevator" (most have them), there may be a small problem with some models. For example, the MOssberg 500 shell elevator doesn't feed them very reliably (unless you pump the gun VERY fast). In order to solve this problem it's easy to modify or extend the elevator to allow more reliable feeding. Though there is still a chance that the shells may 'tumble' in the receiver before being chambered, thus remains a slight chance of misfeeding.
These shells are VERY fun to shoot, they're generally cheap, and have a generally light load as well. I like them (even in my mossberg 500). My shotgun also holds the 12+1 minislugs. Sure are fun little slugs, just don't depend upon them in a life-threatening situation.