During my two tours to the Sand Box with the U.S.M.C., we encountered some of the worst conditions weapons can endure. The sand in the Middle east is fine "moon dust" similar to talcum powder. The problem is that when mixed with water or oil commonly used in cleaning weapons systems it turns to a mud like paste. We discovered that the regular issue Cleaner, Lubricant, Protectant (CLP) [which is a Mil-Spec lubricant, sold commercially under the trade name "Break Free CLP".] CLP was contributing to the problem more than fixing it. It is true that we cleaned our weapons daily sometimes two or three times depending on conditions and enemy activity. Our M16/ M4s would function properly as long as they were cleaned routinely. Problems would occur when troops were engaged for prolonged times and couldn't risk breaking down their weapons to clean out all the dirt. We would simply pour in more CLP. An AR-15 type rifle will fire and function dirty as long as it is liberally lubricated. The problem is the more oil you pore down the bolt and into the chamber the more dirt it collects. What we discovered is that using Mobil1 synthetic motor oil usually in a 0w30 or 5w30 works much better than the CLP. At $10 per quart it is on the expensive side as motor oils go. But when compared to CLP or Rem Oil that are usually sold in 6 ounce containers at $5 to $6 it is much more cost effective. We also experimented with it on out crew served weapon systems. We found it to out perform the (Lubricant, Small Arms (LSA) used on the M2 (.50 Cal Browning machinegun) and MK-19 (40mm grenade launcher).
We had a one M2 so close to the courtyard where our LZ was that it literally had to be cleaned, to function properly, after every bird touched down and took off. This presented a huge problem as the frequency of the flights in and out ,crucial to resupply our Battalion, would render the weapon inoperable. We solved this problem with the Mobil1 in a 20w50 weight as LSA is more similar to axle grease that gun oil. Also we began to cover the weapon with a poncho every time we heard a bird in the air or saw the smoke canisters in the LZ. Due to the high security risk and vulnerability of helicopters during landing and take off, OPSEC was in place. This meant we never knew when the next bird was coming in. One of my Marines actually had the weapon system mounted on his turret malfunction and jam during a fire fight. They had just left the wire and the cleaned weapons as was SOP before every patrol. I shared the secret and traded him a bottle of Mobil 1 for a few energy drinks he had received in a care package. He never had a problem again.
I heard a rumor that the Marine Corps had experimented with synthetic motor oils as potential weapons cleaning lubricants. They determined them to be too effective and decided it would bring complacency as Marines might assume that they now had to clean their weapons less. This is not the case. I still recommend cleaning your weapon as frequently as possible. In the Corps we would hold random weapons inspections and any NCO could demand to see the bolt on any junior Marine's weapon at anytime. I also want to mention that we never tested traditional (non-synthetic) motor oil on our weapons but the use of motor oil for cleaning and lubrication of weapons systems has been recognized by the US Military as early as WWII and can be found in numerous field manuals.
Thought your readers might like to know this. Semper Fi, - Sgt. K.A. U.S.M.C.