Durability vs Repeatability

Talking about durability of rifle scopes typically results in opening a major can of worms, so I will keep it short and to the point.
 

Durability refers to how well the scope holds up to being used over time, i.e. a durable scope’s performance does not change in any perceptible manner as it is used.

Repeatability refers to the consistency of controls and adjustments.

Technically, neither good durability nor good repeatability guarantees that a scope is going to work well, since neither one guarantees precision and accuracy. A scope can have uneven reticle adjustments, click value can be off, POI can change with magnification. However, for as long as it maintains this behavior without deteriorating or changing, the scope is both durable and repeatable. In order to make it a good scope, it also has to have adjustments that perform to spec.

Durability is very difficult to discuss since it is by nature a statistical parameter. Only the manufacturers have access to the statistics of how many of their scopes break (and are sent back to them). All the information we typically have is simply anecdotal evidence that is rarely statistically significant. All things mechanical can and do break occasionally. If one scope breaks, it is not necessarily an indictment of the rest of that product line. However, if the person whose scope broke is vocal enough, he can create enough reverberations on the internet to blow up the problem. That having been said, in many cases there is enough anecdotal evidence to provide valuable information. For example, one brand that recently emerged with particularly obnoxious advertising is certifiable junk. The brand I am referring to is “Counter Sniper Optics” and this is a case where there is enough anecdotal evidence to make it statistically important.

Still, by and large, all we have to go on is word of mouth and that tends to be dominated by a few “loud” voices. Over the years, I have managed to coerce a few manufacturers into privately disclosing their return rates, but I swore to keep that information private (and I will not break that promise). All I got out of that is a simple fact that mid-range scopes are typically well-made.

What makes things even more complicated is a simple fact that many riflescope designs go through small quiet changes that are never disclosed to the customer. For example, it is not uncommon for a new product to reveal a design flaw during the first few months on the market. As soon as the maker learns of this and does appropriate Failure Analysis, the design flaw gets fixed. However, if the owners of original faulty scopes are loud enough (and if the manufacturer is dumb enough to provide less than stellar customer service in today’s competitive market place), the reputation of the whole product line can end up tarnished.

Then there are the different failure modes: if your scope is going to fail, you want it to fail catastrophically, so that you know right away something went wrong. The worst kind of failure is the gradual decline in precision and repeatability, since it is often difficult to diagnose until it is too late. Bottom line is that if you want to avoid surprises, check your scopes periodically for precision and repeatability of adjustments.

Lastly, there is a case of unreasonable expectations (yet again). I expect every scope I have to be durable. If it does not hold zero, it is a paper weight, not a scope. However, if it is a truly inexpensive piece, I do not have very high expectations on repeatability, so I do not mess with the adjustments too much. The more I pay for the scope, the more I expect from it. By the time we get to mid-price scopes ($500 to $1000), I do not expect any nasty surprises. For the truly high end stuff, I expect everything to be flawless, since I have just paid twice more money for 10% more performance. The rest of that extra price tag goes into QC.