The reliability of weapons in the field versus at the range is primarily a function of environmental tolerance. Environmental tolerance is simply a measure of how sensitive the weapon is to changes in the environment. A weapon that will operate in or out of water is more environmentally tolerant than one that can only be fired when dry.  The tricky part is that ‘environment’ refers to an extremely wide range of factors. Not only does it include the obvious such as heat or cold; it also includes subtle changes such as how one grips the weapon when firing.  It even includes things such as how much impact the weapon can withstand.

A firearm’s environmental tolerance is largely determined by the design and construction of the weapon. However, there are several areas where the operator can significantly impact reliability. This article addresses weapon handling, cleaning, and lubrication.

“Handling” literally means how we handle the gun. To use an extreme example, if every time the gun is set down, it is simply thrown at the ground, eventually something is going to break. And even if nothing breaks the odds of the weapon retaining zero are slim to none. However, if we are careful to set the weapon down gently, the gun is much more likely to work when and how we need it too. Of course, in the field, things happen. Weapons get dropped and banged about, but we improve our odds of having a weapon that functions properly if we treat them as gently as practical.

Handling also means being careful about exposing the weapon to environments that are likely to cause problems. Taking care to keep dust covers closed and always setting the weapon on top of your pack, rather than directly in the dirt are both examples of limiting the weapons exposure to the environment. There are some units that choose to use various types of covers for their weapons to limit environmental exposure. These covers range from plastic muzzle caps that keep foreign material out of the barrel to tear away plastic bags that encase the entire weapon. What is suitable for your weapon depends on the conditions you operate under.

It is not just the weapon itself that needs to be handled properly. Both magazines and ammunition are critical to the function of a firearm. Bent magazine lips or ammo coated with sand are both certain to cause malfunctions. All components must be handled with as much care as is practical.

Magazines are often one of the most fragile parts of a firearm. If you have magazines in your vest or belt pay attention to how you treat your vest or belt. Climbing over obstacles or around vehicles your kit can get banged about pretty good. Kit left on the ground can get stepped on. When you get down time make it a point to check the condition of your magazines. Don’t just look at them unload and reload a few rounds to make sure the follower is tracking properly. When it doubt throw them out.

Even if your new high-tech polymer magazine survives being stepped on, the ammo inside of it may have the case wall dented. Ammo needs to be treated just as carefully. Don’t leave ammo cans in the hot sun if you can help it. High temperatures cause the primer and propellants to age faster. It will probably never cause you a problem, but who knows how that ammo was treated before it got to you. Be careful to keep your ammo dry and away from cleaning oils and solvents. Yes, military ammo is sealed, but do you really want to bet your life on the quality of the seal? If you repeatedly re-chamber a round toss it. Repeatedly re-chambering the same round can force the bullet back into the case. Again, military cartridges are crimped to prevent this issue, but why risk it if you don’t have too.

The next issue is cleaning. While it is true that most modern firearms will function for quite some time without cleaning, it only hurts reliability to leave a weapon dirty.  At the end of the day, firearms are simply machines. Machines run better when they aren't filled with dirt and carbon build-up. This type of fouling serves to increase friction inside the weapon and excessive friction causes malfunctions. Fouling can also build up on parts and prevent them from fitting together properly. The result of parts not fitting together properly can be a weapon that won't go fully into battery or that a sear will not lock up fully and will let a round go unexpectedly. Neither are desirable outcomes.

A gun does not need to pass the white glove test to be reliable. A more practical standard is that you shouldn't be able to find any carbon build up or gritty material anywhere on the inner workings of the gun. If you don't have time to clean the weapon completely then just pull out the main parts and quickly wipe them down with a clean rag and add a few drops of oil. Half-clean is better than all dirty.

The last area to address is proper lubrication. A fighting weapon should be lubricated regardless of the environment.  To some degree is doesn't matter what lubrication you use as anything is better than nothing. And despite what some manufactures would have you believe there is no magic lubrication that will prevent all malfunctions.

If you are using a 'wet' lubricant don't under or over lubricate. A good way to apply wet lubricants is to use a small bit of cloth saturated with the oil. As you assemble the weapon wipe each part down so it is covered with an even film. If you are lubricating without disassembly a few drops worked into the action will generally do the trick.  

If you are using a dry lubricant or one that will dry after application then follow the manufacture's directions. Also, don't believe the hype about dry lubricants being the cure all for sandy environments. There are pros and cons to each. 

If you want to maximize reliability in the field there are three simple rules to follow:

1.) Treat the weapon, magazines, and ammo carefully.
2.) Keep the weapon, magazines, and ammo clean.
3.) Keep the weapon lubricated.