The 870 has some design issues, exacerbated by quality problems in recent production guns, that mean it is possible for the 870 to jam to the point that you will have to disassemble it to fix it.
There’s also the short-stroking issue endemic to all pumps.. which is why more and more militaries and police entities are moving to semi-auto shotguns. The Army is replacing all their pump guns and the Marines have just about finished replacing all theirs.
My 870 is 1970’s vintage - and after putting a few hundred rounds through her, she’s not jammed on me once.
I’ll wager that the “short-stroking” issue is more due to operator malfunction than to any generic defect of the weapon; i.e.: not enough practice to develop muscle memory - or just not enough “muscle” effort to properly eject and rack a round in the chamber.
So which semi auto was selected. I have an S&W pump 12 that belonged to my dad.