Far and away the most common problem I see when instructing is lack of proper lubrication. This goes for civilians, LE, and military. Of the groups I train on a regular basis military Spec Ops definitely understands the importance of lube the most but it is still common to find weapons not lubricated properly. And what I mean by properly is having lube in/on the working parts of the weapon.
Many weapon systems will not tolerate lack of lubrication and continue to function for any length of time. The US military M16/M4 family and M9 pistol are prime examples of two weapons that do not work well or for long without lubricant. Another example is tightly fitted custom or semi custom 1911 pistols. Simply put these weapons and others REQUIRE lubricant to function reliably – no way around it.
There are weapons that do not require a lot of lubricant to function reliably. The AK family and Glock pistols come to mind. Also HK does extensive testing for reliable function with little or no lube so by and large HK weapons are very forgiving to lack of lubricant by design. However too many shooters rely on that as standard operating procedure and don’t assess the situation correctly; these guns are designed to continue to function without lube in EXTREME (not daily) conditions but every weapon works better with lubricant.
The golden rule in weapons lubricant is you can run a gun dirty and wet, but not dirty and dry. Truer words have never been spoken about weapons lubricant. Guns always work better the cleaner they are but most modern designs are far more forgiving about carbon fouling than they are about lubrication. Remember to keep it lubed always and clean it when you can and you will be much better off over the long haul.
The topic of keeping a weapon dry in desert environments comes up quite often. Sand is the ultimate enemy of guns and can wreak havoc with modern small arms. I have been part of extreme weapons testing and can tell you that I have no doubt in my mind that in sandy environments you are much better off with a gun that is lubed than one that is dry. Having sand coat your small arm like a sugar cookie with some lubricant still in place is a better situation than a completely dry weapon in a sandy environment. Your weapon may still malfunction but not anything like it would if it was bone dry. It is unbelievable how non functional a dry weapon can become in an extreme sandy environment. It will become manually operated at a bare minimum. Your best bet for a functional weapon in extreme conditions is to keep it lubed and keep it covered. It may take longer to employ the weapon depending on the cover used but it will most likely work when you need it to.
Last thing I will cover is choice of lubricant. First off any lube is better than no lube. Just because you don’t have your favorite synthetic gun oil doesn’t mean you don’t lube your weapon. With that being said in my experience the thin light lubes like WD40 and RemOil are to be avoided. They will provide a rust barrier and that is about it; they are not suitable for moving parts lubricant. There are a lot of lubes on the market but my personal favorite is FireClean.
Please don’t get your panties in a bunch since I did not mention your pet lubricant. I am sure there are dozens of excellent lubricants on the market I am not aware of that do a great job; I am simply stating what has worked for me with very good results for many years. In parting I would remind you to remember two key points about weapons lube; any lube is better than no lube and you can run a gun dirty and wet (or lubed) but you cannot run one dirty and dry. Abide by these two rules and they will do you right