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 Mossberg Shockwave firearm or 500/590 series shotgun.
http://www.nxtbook.com/nxtbooks/nra/.../index.php#/40
https://www.americanrifleman.org/art...nch-shotshell/