Aguila is producing some very interesting shotgun shells for use in your pump, over and under, side-by-side, or single-shot.  The Mini-shell is a reduced length (and recoil) loading (No.7-1/2 shot ) for birds or clays, and tactical (slug or combo -- 7 no. 4 buckshot and 4 no. 1 buckshot).  The advantage of the Mini-shell is shorter length -- 2 inches instead of 2-3/4 inches -- and that means at least one or more additional rounds in your magazine tube.  Shorter shells also mean less felt recoil.  Since engagement ranges with a shotgun aren't very long even with slugs (about 50 to 75 yards maximum), you shouldn't see much difference on the target.

 

Mini-shells don't suffer as much from the problem of over-penetration in a typical building to the extent a standard 2-3/4 inch shell loading does.  The only problem is whether your pet pump gun will feed the shorter Mini-shells reliably.  To know is to buy a box of the different loads and run them through your pump shotgun to check if it will feed the shorter rounds reliably.  Aguila's website has a list of pump guns that feed their shells reliably.  However, just because your shotgun isn't listed doesn't mean that it will or won't feed them.  That is revealed in real world testing.

 

Notice that the self-loading shotguns are not on the list.  Mini-shells typically won't work in a conventional self-loader.  They usually don't generate enough gas or recoil to work the action reliably and they may have feeding problems from the magazine. 

 

Mini-shells run about $18 for a box of 20.