We are a high-volume indoor range in Las Vegas and see things happen to guns that are not supposed to happen, regardless of them being "cheap" or high quality. The things we see continue to surprise us because when we think we've seen it all, something else happens. Also, parts breaking and weapons being taken off line is, in my opinion, not due to the lack of care that the staff provides. We keep records on each individual weapon to include when it was cleaned, any parts replaced, why parts were replaced and any noticeable wear to keep an eye on.
When we opened our range in October of 2012, we started off with my personal Mossberg 500's, Remington 870's, SPAS-12 and Benelli M4. The Mossberg (I can't recall which actual SKU) had a longer barrel and was a newer production shotgun. The Remington was an older police trade-in that I purchased as group. These were older guns that mostly steel parts (not the plastic or aluminum trigger housings), wood furniture and a parkerized finish. The Benelli M4 was my just recently acquired SBS and was factory new when put on the line. The SPAS-12 was purchased at our retail gun store as a trade-in from a customer. I didn't know anything about round count or how well it worked or didn't work. Since opening, we've expanded our line to the Saiga-12 (SBS), VEPR-12's (full-auto) and Chinese double-barrel coach guns.
I am not a "shotgun" guy per say as I never spent much time tinkering with them other than a basic cleaning. Some of my staff are really into shotguns and others are not but I did send them all off to factory armorer's class to make sure they are all on the same page. That being said, I've always left the maintenance, cleaning and repair to them.
When we initially opened the range, all the shotguns performed as expected. They were getting light to moderate use but as we grew bigger, the shotgun use increased faster than other weapons. I couldn't understand why so many people were interested in the shotguns but after being in business for a while and talking to customers, they want to feel that racking of the pump and hear the "ch-cha" that they've heard all their lives on TV, movies and video games. I've heard that noise for most of my life and it didn't click initially with me as I didn't realize how many people have never seen a real firearm up close and personal, never mind even touching one. I myself enjoy the Benelli M4 as it has, in my opinion, a much smoother action and less recoil. I would try to offer the Benelli to customers with a smaller stature or females to lessen the felt recoil but SO many still wanted to experience the feel of a pump-action shotgun.
I will have to more details as to what parts break in our Mossberg's and Remington's but it's fair to say that the "low budget" model of each lasts about the same amount of time on the range. One doesn't outshine the other and they all last about the 2-4 weeks on average before suffering from parts failure that takes the weapon off the line. Forgive me for lack of knowledge on the weapons but the "forks" that actuate the cycling are what break first and most often. The ejectors fail on both at about the same rate and we've actually had receivers split. Barrels have never failed though after a ring or two down the bore, the barrels are pulled from service. I have spoke with rep's from both Mossberg and Remington and I could tell they didn't believe me or implied that we don't how to maintain them. I don't blame them for their opinion and didn't take offense to it as I would probably say the same thing.
One thing that my armorers have said about the repairing of Mossberg's and Remington's, the Remington has a rivet that has to be drilled out re-installed in order to make it work properly. I "believe" the part was the ejector rail (??) on the Remington but if that's it, then it has to be drilled out re-riveted. We don't experience that issue with Mossberg's. When installing the forks on the Mossberg, it's not a just a simple install of the forks but they have to be "fitted" to the action to work properly. I don't know if that's due to receivers that stretched or become out of spec due to high round counts.
We are no longer repairing the Mossberg's or Remington's at this point after determining how much is spent on repairing them, ordering new parts and it's just not worth the cost of repairing when new shotguns can be purchased at a cheaper price. We used to demil the shotguns and destroy them but I convinced my wife to let the staff purchase them for $25 as "tinker" specials because the know how to fix them and they can do it on their own dime at their convenience.
As for the Benelli, that is the longest working shotgun in our inventory. It has been on the line since day one and after inspecting the records, it actually did suffer one parts breakage. The part that broke was the rear sight and not related to any shooting or over-use (staff member dropped it). It may not be used quite as often as the pump-action shotguns but it goes on the line daily and there are plenty of people who want to shoot it thanks to all the video games that it's featured in. We've used 00-buck, "light recoil" buck, birdshot and frangible buckshot and it eats anything that we give it and never fails to cycle. The Marine RSO's all have prior experience with Benelli M4 and really love it and the fact that it continues to work and work always leads them to boast about how well the Marine's choose their weapons.
The Saiga-12 has always been particular to which ammo we fed it. I've tried to tune it the best I could by making sure the gas port holes were correctly aligned and opened up for the additional gas needed to cycle it with a 10" barrel. We added all the usual aftermarket gas pistons, springs and receiver "tuning" to get it function with other ammo but it will only cycle with higher q 00-buckshot.
Since putting the VEPR-12's on the line, they have run flawlessly. We did a post sample (full-auto) conversion on four of them for a demonstration for an agency that decided not to purchase them after it was all said and done (I believe budget issues came into play). Other than the conversion, we did no modifications or "tuning" to the shotguns whatsoever and they continue to and run. They are used daily and I have the RSO's give free time on if for guests with birthdays and bachelor/bachelorette parties so it does get considerable use every day.
The poor SPAS-12 is hated by ALL the staff. I did state that I don't know anything about it's previous history but it is not a reliable shotgun in our experience. The counter girls have to verify that it's in service, the armorers have to look at it and the RSO's have to apologize when it doesn't cycle properly. We have two of them available and they both function about the same when it comes to reliability. The other issue we have is parts availability. I don't know the part that breaks but only one person makes the part (it seems like something that he casts out of resin) and it can take anywhere from 2 weeks to 2 months (or longer) to receive it. We don't try very hard to push it but there are die-hard movie and video game fans that MUST shoot it to complete their lives
Lastly, the Chinese-made old Western reproduction shotguns. They are not of the highest quality but they are cheap enough to purchase to cannibalize from in order to make others working again. The springs that close the actions usually fail first followed closely by the wood stocks and hand guards cracking. The wood is very lightweight and soft. It dents easy and the stain/varnish don't last long either. We use them as SBS's for the customers who want to get the feel of a small double-barrel shotgun that the "cowboys used the Old West".
That sums up in minor detail about the function of shotguns on our range. I will get better details and pictures with questions you provide and try to update this post as often as possible. One thing that I can say about the Mossberg and Remington pumps is that the older police trade-in's (all steel parts) lasted the longest BY FAR of any of the other pump shotguns. We still have two that were going to be sold off but my staff knew they were mine and made sure they got put in the vault in my office so nobody would purchase them. I will have one of the armorers punch the rivets, replace all the worn parts and reparkerize them so I can eventually bring them back home and rescue them from the range.