Y'know how pump action shotguns have a reputation for durability and reliability? Did some research on that, specifically the Mossbergs (cuz Remington seems to have been in a clusterfuck for a while now. How do you even tell which 870s are good or not???).
First off the most vulnerable part seems to be the action bars. Battlefield Vegas's post on arfcom makes that pretty clear:
https://www.ar15.com/forums/Armory/...n-Benelli-and-Chinese-clones/1-474035/?page=1
"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."
First off for the action rails, looking for other reports on other forums it seems like they tend to blow apart at the spot welds, brazes, pins or whatever keeps them connected to the forend:
https://www.thehighroad.org/index.php?threads/whos-seen-or-had-a-broken-mossberg-500.225888/page-5
"I ripped the action bars from the forearm ring once and it was a quick fix at my gunsmith. The spot welds broke so we silver soldered it back together. Other than that no problems with over a dozen Mossberg 500s." (Only put this quote here but there are plenty more describing the same thing).
That specific problem looks to be easily repairable, so while it might be a huge issue for a big rental range like Vegas where they need the guns in working order 24/7 to be used by the lowest common denominator it's probably less of a problem for the individual, trained user.
Second the ejector failure. I'm not gonna lie I haven't researched that very much, but that seems to be a common wear part on many guns, and on the Mossbergs in particular they seem easy to replace so that's in the same category as action bar failure (non-catastrophic, user replaceable/repairable).
Now the big issue: receiver splitting.
https://mossbergowners.com/forum/index.php?threads/maverick-88-cracked-ejection-port.20916/
If you look carefully at the design of the gun (
https://www.youtube.com/watch?v=9itbuBE2sq0 nice cutaway animation here) the cracked portion is a very thin, non load bearing part of the reciever above where the action bars run in and out. Given that it seems to not be load bearing and that this catastrophic failure looks to be quite uncommon my personal theory is that this seems to be caused by burrs or poorly fitted action bars wearing into the receiver. The Battlefield Vegas thread alleges that "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." It's doubtful (to me at least) that it's because of receiver stretching. The bolt locks directly into the barrel extension so it shouldn't stretch longitudinally like Lee Enfields supposedly do, and if it's stretching vertically that would obviously ruin the cycling as the receiver rails wouldn't be straight & uniform anymore. What seems likely is just that the tolerances suck and the replacement parts might show up a bit out of spec, and if that's the case then it is likely messed up fitting, out of spec parts, burrs, etc. are causing this cracking issue (notice how the crack in the photo seems to correspond with where the action bars would be and in the direction in which they run) which is why it only occurs on this specific, very thin portion of the receiver.
Additional links:
https://www.reddit.com/r/Shotguns/comments/1murizn/action_smoothing_maverick_88/
This link has round count stuff (30,000, 15,000, blah blah blah)
https://www.canadiangunnutz.com/for...een-a-mossberg-500-590-receiver-fail.2061448/
Obviously not gonna take everything on these forums as 100% fact but if it makes logical sense it's probably true. Now do any of YOU guys have experience with shotguns and their longevity/durability?
