I ran a combat shotgun class a while back. Had a fairly wide array of shotguns present in the hands of the students.
Had 2 Mossberg 500's; both ceased to work during the warm-up drills that started the day. Major feeding issues. One of the guys borrowed my old HK-marked Benelli M1, and the other borrowed a Nighthawk Custom 870 off another student. Both of those ran flawlessly.
Had 2 Mossberg 930's in the class. One ran perfectly, the other one had some hiccups here and there, which we traced to it being dirty and bone dry.
Had a UTAS UTS-15. It wouldn't function from the get go. Even worse, that thing is so confusing I couldn't diagnose the problem!
Half the class ran 870's........no issues with any of them that weren't due to operator error.
The lone Winchester 1300 Defender ran fine, as did the only Remington Versa Max. That Versa Max is FAAAST........I ran 6 rounds out of it as fast as I can out of my M4 carbine in 5.56. Fast, smooth and light recoiling.
I ran a 14" Wilson Combat/Scattergun Tech 870. Needless to say, she ran like a champ.
No Benelli pumps or M4's were present, or Mossberg 590's. No old school Ithaca 37's........love them thangs.......
I've seen every type of shotgun you can think of fail, just as with any weapon system. On pump shotguns (of any brand name), the majority of the problems I've seen were user error. On autoloaders, most problems are related to the ammunition, e.g., not "powerful" enough to properly cycle. But, I have seen shotguns from every company have legitimate mechanical malfunctions that had nothing to do with the operator or the ammo. This includes my beloved 870.
With that said, I have found the Remington 870 to be the most rugged and reliable combat shotgun on the market. I have not found a single issue with the Mossberg 590, either. The only reason that I put the 870 in front of the 590 is that I see WAAAY more 870's than I do 590's, probably a ratio of 15:1. For all I know, the 590 could be the better gun, but I don't see enough of them to accurately compare them to the 870. Years ago, I borrowed a 14" 590 while attending a week long Shotgun Instructor workshop; she ran like a champ and I aced the qual course with her.
I've yet to see a problem with the new Benelli M4, but I have had less than 10 of them come through my class. I'm contemplating buying a 14" model, if I do we'll see how she runs.
If you are in the market for a Remington 870, check and see if there's a shop in your area that does a lot of LEO business and look for a trade-in Police model. That's the way to go, quite a few differences between the Police model and the standard or HD models. I'd rather have a used Police than a new HD. Alternately, you can "upgrade" your 870 to a Police, or have it done. My 14" 870 started as a beater "standard" model that was sent to Scattergun Tech. They chopped the tube, installed ghost ring sights and performed all the upgrades to Police model specs. I later replaced the 12" barrel with a Remington 14" barrel with fixed Modified choke. If you don't wanna go that far, at least make sure that your lifter has a flex tab. If not, that's a cheap and easy part swap that you can do yourself.
Here's the differences between a Police and Express model:
• 870 Police shotguns go thru a special 23 station check list – ranging from visual inspection, functional testing, test firing, and final inspection.
• All Police shotguns are assembled in a “special build area” at the plant in Ilion, NY. This section is secured and serves only to build LE and Military shotguns, with the same factory personnel working at that assignment each shift.
• All parts that enter the “special build area” are visually inspected by hand to ensure top quality and functionality.
• Due to heavy recoil in buck and slug loads, all 870 Police guns have a longer magazine spring which ensures positive feed and function.
• A heavier sear spring is used to generate a reliable, positive trigger pull between 5 and 8 lbs.
• A heavier carrier dog spring is used to ensure when the carrier elevates the shell, it will be held there until the bolt can push it into the chamber. This ensures positive feeding when using heavier payload rounds.
• Police shotguns do not have an ISS (Integrated Safety System) which is a locking mechanism on the safety of commercial shotguns. This type of locking mechanism can cause delay to an officer who needs the weapon but does not have the appropriate key. LE shotguns have the standard, proven, cross bolt safety.
• The fore-end on the Express model is longer and not compatible with many police shotgun vehicle racks.
• The Police shotguns utilize the heavy duty SPEEDFEED Stocks and Fore-ends.
• The Express model will not allow for the addition of an extension tube without physical modification to the tube and barrel, which can nullify the warranty.
• The Express model has a BEAD BLAST BLUE finish while the Police models utilize either High Luster bluing or Parkerization.
• The Express model utilizes a synthetic trigger housing while the Police models use a compressed metal housing.
• The Police shotgun barrel is locked down with a “ball detent” system in conjunction with the magazine cap vs. a lesser grade “synthetic magazine spring retainer” lock down as used on the Express system.
• The receivers used in Police guns are “vibra honed” to smooth out rough finishes and remove burrs before parkerization or bluing.
• Police shotguns use machined ejectors and extractors, as opposed to powdered metal cast which are utilized on the Express models.
On the 2 Mossberg 500's that failed in the first 20rds during my last class, neither were due to user error. I attempted to run each gun myself......nuttin' doin'. On one of them, the shells would not feed from the tube. They just stayed there and refused to leave. When that happened, it would not function or fire a single round. On the other one, it would malfunction on the average of every 3 rounds or so. When the lifter/elevator would present the next round to the bolt to be fed into the chamber, they would either come up at an angle, or not high enough, or both. When then would happen, the bolt round catch the round at an angle and refuse to feed it. On both guns, we tried to run them with at least 4 different factory 2 3/4" birdshot loads, as well as high brass 00 buck and slugs.