Just noticed this:

The Dec. 2017 issue of the American Rifleman contains loading data for a 2" twenty pellet #4B 12 gauge load on page 39.  This is data for a simple 1100 fps roll crimped load, with a 1.75" loaded length, for those wanting to pack the maximum number of low recoil close range buckshot rounds into their Mossberge Shockwave firearm or  500/590 series shotgun.

http://www.nxtbook.com/nxtbooks/nra/ar_201712/index.php#/40

Hard to say.       Some guns have a lot of trouble cycling the Aguila Mini Shells without being modified.  I think there are some options out there for various guns but I don't have any experience with them at this point.  The hang up seems to be that the shorter shells tip up more when being fed into the action and occasionally hang up during the process.