Found this old earth shotgun early on a play through with the legendary stats already set and really enjoyed it. Staggering and shattering in air very nicely and lets the flechette rounds do near maximum damage to most targets. I added the reckless fourth level slot to it and it fires almost as quickly with a reload between shots as it did prior with the pump action. With one perk point invested into rapid reloading there is no noticeable difference in fire rate between shots with reckless or without. If you time it right you can even skip pumping the shotgun after the shell reload. Staggering works almost every time you fire it, the flechette rounds cause bleeding and if you didn’t take down your target with the first shot the second one will.
Only downside is the ammo is rare and expensive to manufacture, but range is better than you’d expect and even just clipping a low level enemy at forty yards will usually eliminate a threat. It is unbeatable in ship combat and fighting in mines and inside facilities on planets, and will melt through most creatures that decide to get close to you.