... It's no secret that one of the traits of firearms and perhaps more so handguns specifically that draw us to them is the idea that with care (even normal, common usage and care), these are items that most of us fully expect to last WELL beyond our lives and maybe even the lives of our children.
Maybe we have no right to expect that... but so many of us have firearms from our Grandfathers and at this point, it's almost natural.
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Yours is a very common reaction and opinion.
It just might be that a lot of people have an unrealistic, but understandable, expectation of the service life of many firearms, though. We can see many examples of such firearms that have been passed down through generations, right?
However, how much actual "usage" have they actually received?
I have a copy of a FBI report of the end of the 80's when they did some testing of many of the current crop of service pistols of that period. Most had aluminum frames. It was noted that a couple of the alloy pistols of the time, made by S&W and Sig Sauer, could develop frame cracks by 10K rounds fired. It was also noted that the expected spec for "service life" of some military pistols (here and elsewhere) was only 5K rounds. In other words, an aluminum alloy frame that lasted for 10K rounds had just about doubled the required service life.
By contrast, the agency noted that the HRT's service pistol of the time, the Browning HP, had demonstrated an average service life at that point of well into the 80K range, if I recall (without having to go dig out the article in that manual from '90). Well, that's steel for you.
In the 90's cops (and private owners) apparently started shooting more, and it wasn't long before they started requiring "more" from their pistols. The gun companies that saw a lot of major LE business started making aluminum-framed (and plastic) guns that would meet stated requirements for longer service lives.
Now, it's not uncommon for LE duty weapons to normally get replaced on some schedule of approx 5-10 years. Various reasons. Some agencies, especially those who maintain pretty large inventories, sometimes keep guns in-service as long as they can be maintained and kept within proper conditions and meet factory spec, which might be for a long time ... depending on how much they're actually fired, of course.
That can get expensive at some point, with "rebuilds" often costing enough that it may be considered financially unwise to keep pouring money into a "used" gun that might better be spent on a new gun. (Sounds like a used car, huh?

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Slides and barrels are expensive (if not covered under a warranty replacement program). Ditto drawbars and hammer assemblies for 3rd gen guns. If you originally paid $500-$700 for a gun, and then you need to spend another $200-$300 on parts and assemblies as guns age and are subjected to normal wear & tear? How about paying the armorer for the bench time (and especially if it's paid as overtime, because the armor position is part time and something done in addition to a regular assignment)? A new gun starts to look very attractive, budget-wise, over the long term.
At some point, some number of heavily used (or simply heavily abused) guns may reach a point where the frame can't be kept within factory spec, and obviously then the whole gun has to be taken out of service and replaced.
I once spoke to a FBI agent who said they'd really liked their SIG 9mm, but the day had come when the agency armorers had said the gun had reached the point when they could no longer keep the gun operable and within factory spec, so it had been pulled and replaced with the currently issued Glock.
I remember being told by a S&W factory repair tech that when they'd built the early 3rd gen guns (that our agency was still using), they'd never expected an average agency would ever end up firing more than 5K rounds through them over the course of a career.
FWIW, according to some manufacturer info of the time, the "average" private owner of a handgun probably wouldn't fire 500 rounds through a gun they owned during their whole life, and it wasn't exactly uncommon for some owners to still have part of their first,
original box of ammunition left after they'd owned guns for several years.
Somewhere I have a gun magazine I kept from back about '79, in which a lightweight Colt Commander had been fired for an extensive torture test ... of 5000 rounds. I owned one and often wondered about how long the aluminum frame would last, since I was an avid handloader and shooter. I foolishly ended up trading it for an all-steel "Combat" Commander.
Nowadays many owners who enjoy frequent shooting as a pastime would probably think of shooting 5K rounds as just getting a gun broken in and warmed up.
Lots of people are apparently expecting more of their guns, and are shooting a lot more rounds through them. IDPA (and Glock's GSSF) have probably generated more interest among many of the "average" handgun owners to get out and shoot more.
Training classes and schools are growing at an amazing rate. The last couple of small storefront guns stores (not open all the time, since the owners have other jobs) have advertised training classes for customers. The introduction of classroom & range training for CCW licensees is seemingly another growing industry, too.
Cops have been shooting more, overall, too. I've read, heard and learned of increased shooting regiments and training occurring. I've been told by some different gun companies (as an armorer) that there's been a slowly growing trend of agencies requiring more training, and subsequently placing more demands (wear and tear) on the guns they're buying and using.
Over the course of several years, attending various armorer classes, I started hearing of increasingly more frequent factory recommendations for the inspection and replacement of "wearable parts". "Wearable parts" are defined (by at least one company) as parts which are expected to wear during normal us, and their replacement isn't a warranty consideration.
Now, go without replacing some wearable parts for too long, and then have the gun become battered and damaged? Don't be surprised to be told it's not a "warranty problem".
On a related note, recommendations for some spring replacement intervals were becoming more specific over time, too.
I've listened to different gun companies who have been telling armorers that some of their continually revised and constantly improved guns were offering longer, practical service lives. Well, that's progress, right?
I'll guess we'll see how well the modern aluminum-framed guns are going to be lasting for "generational use", as well as the plastic-framed guns. I certainly have a lot of them in my safe which my son is going to inherit, and probably pass along to another generation. He likes the older revolvers, shotguns and lever rifles, though.
BTW, even in the revolver days of LE, I listened to various armorers discuss how they sometimes had to work to maintain a variety of S&W and Colt revolvers, especially if fired with more Magnum than standard pressure loads. Remember the introduction of the L-frame and GP-100? The performance/endurance package on the 629?
Don't forget we have some improved materials, metallurgy and heat treating that weren't available in previous guns. Better manufacturing, too.
So, we may have some cherished perceptions and expectations of how long the average "gun" may last over generations, but that doesn't mean those expectations are going to be reasonable. Did our fathers, grandfathers or great grandfathers shoot 10K or 20K rounds through their deer rifles? How about that war trophy 1911? How many rounds do you suppose some GI in WWI/II, the Korean or Viet Nam wars was able to get their hands on to use, anyway?
Sorry for the rambling. I totally understand and appreciate your meaning, but all equipment has a practical and useful service life, and that's under optimal conditions where it's not subjected to unreasonable abuse or neglect ... and it's maintained.