Nice shotgun, that is not one you load with bird shot and take out to the fields!
Truly, the Remington 870 Tactical Magnum with Knoxx Recoil Reducing Stock is an AMAZING weapon! Even though it has an 18” barrel, the fixed imp cyl choke does help with holding the spread pattern fairly well within 25 yds. But, of course, this is no bird gun.
I have seen a few posts from folks who know about the Knoxx stock, and I would just like to add to them. This four stage synthetic stock should be standard equipment on defense shotguns IMO. It literally makes a 12 gauge painless to fire, even the smallest of persons could handle the stoutest of 3” magnum shells with this stock. It is perfectly legal to install this pistol grip stock on an 18” pump, and it reduces recoil so much that one can fire the weapon one handed at full arm extension, although there is no reason to do this except to demonstrate the efficiency of this stock.