"Pour point and flash point are about as helpful in understanding an oil's temperature reliability in a gun as Versace is to a nun: useless."

~Cherry

Educate yourself - Oils

Oil wedge, hydrodynamic lift, hydrodynamic bearing, stribeck curve, babbitt bearings, rebabbitting

Higher velocity moving parts - especially spinning parts - are able to achieve a 'hydroplaning' effect by riding atop a film of fluid, allowing them to last 100x longer than parts not achieving this.

Oils - The When, Why, and How

 

Oils are able to perform brilliantly when paired with the right machine. Modern car engines routinely have lifespans that reach over a billion rotations, especially with regular maintenance and oil changes - but this accomplishment would be impossible with grease.

 

Oils are able to accomplish this for one reason: hydrodynamic lubrication. This regime is achieved with a combination of fluid + movement. To elaborate, it's a combination not only of the velocity of moving parts, but also both volume and viscosity of fluid. If minimum thresholds are met, those parts can achieve 'lift off' and begin riding on top of that fluid film in a manner, again, analogous to hydroplaning your car.

 

In general, this is harder to achieve in sliding systems because of the back-and-forth nature of their dynamics, which require stop/start motion. Consequently, no matter how perfectly matched an oil is to a sliding machine, that part will go in and out of the hydrodynamic regime at the beginning and end of every cycle. The better paired an oil is to a specific sliding part, the longer it can stay in the hydrodynamic regime, but it will unavoidably fall out at some point at the extremes of that course of travel. And if in an unsealed system, the oil will flow out.

Hydrodynamic lubrication is far easier to achieve in spinning parts, such as bearings, which operate for very long periods of time in the same direction, often at extremely high speeds. In these cases, at least one metal part spins fast enough so that the force of its movement creates a 'wedge' of fluid flowing between it and another metal surface. In effect, this removes these parts from metal-to-metal contact, both minimizing friction and maximizing the lifespan of these parts.

Given that our guns don't use an oil pump system, and that they have a back-and-forth sliding dynamic, there is no way to keep them in the hydrodynamic regime for the entire course of travel. Complicating the challenge of achieving 'lift-off' is one of the key principles of tribology: the "Stribeck Curve". Essentially, it states that the lighter the fluid, the faster parts have to go to achieve that lift-off, get separation between moving parts, and reach the hydrodynamic regime. While this is a simplified explanation, it's a key element in understanding the physics behind why oils are not the appropriate lubricant for guns - especially light oils.

 

However, what complicates this even more, is that our guns are unsealed systems - even freshly applied oils will have a very strong tendency to squish out the sides and away from friction surfaces before lift-off velocities are reached.  And again, the lighter the oil, the worse this effect.  Instead of achieving a 'hydroplaning effect', light oils will simply allow moving parts to grind along against each other in more of a 'whetstone effect' for a greater portion of this travel.  

Striebeck Curve, boundary lubrication, mixed regime lubrication, hydrodynamic lubrication, oil viscosity friction

The Stribeck Curve explains how friction between moving parts is affected by oil viscosity, load, and speed. For guns, just remember: the lighter the fluid, the worse the lubrication.

This principle is also a key reason behind why you may have heard that "90% of the wear" in your car occurs at start-up, and during stop-and-go traffic. Because oil is designed to flow, when your car is not running the oil naturally drains with gravity, away from bearing surfaces. Additionally, remaining oil is often pushed out by the weights and forces exerted

Wear in a bearing, stop-and-go traffic car wear, wear and tear stop and go

Without sufficient velocity, the bearing cannot create the 'oil wedge' underneath it to separate the metal surfaces.

by metal parts when they're at rest, or while they're moving slowly. At start-up, those parts are experiencing that same 'whetstone effect', where there may be a little residual lubricant, but until they're fully separated by a fluid film, they grind against each other, causing wear.  Similarly, while these parts may be fully separated at highway speeds, as you bring your car to a stop, eventually those parts slow down enough to drop out of the hydrodynamic regime, and again experience metal-to-metal contact.  This is why driving your car at 70mph causes less wear than stop-and-go traffic.  

 

These realities of physics are the fundamentals behind why oils are not the most appropriate lubricant for guns - they simply lubricate at a lesser level by merely reducing friction during metal-to-metal contact, rather than separating those surfaces entirely.  It does allow your gun to function, where a lack of lubricant would shut it down.  The consequences, however, are that oils, especially light oils, can actually increase the wear rate of your gun dramatically over proper lubrication. 

 

If you want evidence for this, simply open up your own guns and look at the wear.  If oil was doing what a hydrodynamic lubricant does best, you'd have tens of thousands of rounds on your gun before noticeable wear appeared on the rails or bolt assembly. Instead, most of us have guns with levels of visible wear at a couple thousand rounds that a car motor wouldn't have after a million. Part of this comes down to machine differences, but part of it most certainly comes down to using the wrong lubricant for the job.    

Oils - The What

 

In understanding what you're looking at with an oil, they're generally assessed on several key properties, including thermal stability, oxidative stability, hydrolytic stability (stability around water), volatility, polarity, and what's known as the "Viscosity Index", which is how much change you'll see in the viscosity of an oil as the temperature changes. In understanding viscosity, think of it as how syrupy something is - water is very low viscosity, honey is very high viscosity.  Viscosity Index (VI) measures this change in viscosity with temperature changes - the higher the VI, the less changes you'll see. Typically, the more you heat an oil the thinner it will get, lowering its viscosity - this can cause severe problems in machines that may start cold but get very hot quickly, like cars and guns.  So a high Viscosity Index is generally desirable in gun lubricant.  

 

Two other key properties that are especially important to cover on the topic of guns, are what is known as the "Pour Point", and the "Flash Point".  The reason this is so critical, is because these two numbers are not only commonly misunderstood, they're also an easy way for the unscrupulous to get a shooter into trouble - especially on the Pour Point.

Pour Point and Flash Point

 

An oil's Pour Point is not the "Low-end temperature range" - it's the temperature at which that oil ceases to move or flow under gravity. Think honey in a freezer.  It is a completely useless number in a gun lubricant.  Yet, it is commonly offered in a way to suggest that's how cold it can go and still be used.  The reality is that every lubricant has a low-temperature tipping point, where it goes from reducing friction, to adding friction. Its molecules go from slickening a surface, to adhering to it and to each other, like a glue.  The difference between advertised "pour points" and "reliable in a gun" can be as much as 50 degrees Fahrenheit or more.     

Further, every model of gun is different - those with the lowest amount of friction surface and the loosest tolerances are going to have much less surface area for that cold lubricant to apply friction to. A Glock, with its small frame rail-tabs, is simply going to have less area for a cold lubricant to apply friction to than a traditional full frame-rail 1911.  This is also one key shortcoming of standardized laboratory lubrication testing, such as the ASTM series - while they're good for determining coefficient of friction and other standard measurments, they simply do not replicate what occurs inside a gun, in the environments we operate them in. While ASTM testing is still standard and important (we use the G99 pin-on-disk wear test, as it's closest to the sliding forces of guns), we believe gun lubricant manufacturers have a moral obligation to test their lubricants in a standardized weapon with typically tighter tolerances and higher friction-surface areas, and to release the actual temperatures at which their lubricants cease to be reliable. CherryBalmz uses Sig pistols for this reliability testing, because of their high quality uniformity between guns, full-rail design, and global presence in civlian, military, and law enforcement use. When we give you the 'low temperature' on our lubricants, not only will your guns be reliable at these temps with our lubricants, we also are erring on the side of substantial caution - many guns will operate with our lubricants at colder temps than advertised.  

Wear in a bearing, stop-and-go traffic car wear, wear and tear stop and go

"Pour Point" is a useless number in understanding reliability of a lubricant in a gun - it's the lowest temp oil will flow at. Think honey in a freezer.

Flash Point, likewise, is not the "high-end temperature range" of an oil - it's the temperature at which vapors from the heated oil can be ignited. The flash point of gasoline, for example, is -45F. The flash point for diesel fuel is 125F, for Mobil 1 Synthetic 10w30 motor oil is 450F, and the flash point for common canola oil typically exceeds 600F.  These numbers matter, but what they do not do is indicate just how well these oils will maintain their lubrication integrity during the heat of gunfire, or during months of storage or patrol carry.  How fast do they thermally degrade in a gun?  What's their capacity to resist sheer forces? How fast do they thin out and dry out?

 

There is some correlation between flash point and endurance in a gun, but it's rough. For instance, it's notable that the flash point for the CLP issued in the military for decades is 201F, and it's commonly known to quickly dry out in guns.  But it's unlikely canola oil would be a better lubricant than CLP, especially as it has a strong tendency to oxidize and get sticky in open air over time.  So at best, "flash point" a proxy for heat endurance, but it leaves unanswered a host of questions.  However, it is a fairly safe generality to say that the lower the flash-point, the faster it will evaporate from your gun.

Wear in a bearing, stop-and-go traffic car wear, wear and tear stop and go

There are 5 broad categories of oil - groups I-III are refined 'dinosaur' oil, group IV synthetically manufactured PAOs, and Group V 'everything else'

Oil Groups

 

Oils come in five groups, numbered I-V.  Groups I, II, and III are refined 'dinosaur' oils, comprised of hydrocarbon chains of various qualities, generally moving up in quality with the higher the number. A lot of your common motor oils, mineral oils, and older gun oils are made from Group IIIs, and except for the motor oils, often have few to no additives. Generally, none of the properties you look for in an oil are going to be as high in Groups I-III as they will be in groups IV and V.  

 

Skipping ahead briefly, Group V oils comprise the "everything else" category, covering things like vegetable oils, silicones, and esters. It's an incredibly diverse array of oils with an equally diverse array of properties. Some, like Polyolester and other esters, have a great Viscosity Index, but may break down easily from water (poor hydrolytic stability).  Esters broadly have high polarity and natural 'detergent' qualities by crawling along and getting underneath deposits, but if this is not carefully selected for, for exact amount of polarity, it can also severely damage the

ability of boundary lubricants to do their job, getting underneath them and treating them like contaminants. Vegetable oil lubricants are also notorious for breaking down in the presence of water, and having their lubrication properties degrade with heat and oxidation. Silicones, on the other hand, are famously "hydrophobic", and repel water with excellence - but they equally reject additive packages. As a generality, Group V oils tend to excel individually in specific, narrow applications, and especially with esters, will be used as part of an additive package, mixed with Group IV PAOs.

Group IV oils are known as "Polyalphaolephins" (PAOs) - they are by far the most commonly seen synthetic oils, largely because they are often the best at meeting the broadest sets of demands and operating environments. Their molecules are manufactured hydrocarbon chains of extreme uniformity, built to very specific lengths for a given application. Essentially, they have similar building blocks as Groups I, II, and III, but are of far higher quality. And being synthetically manufactured, are far more pure. When you hear motor oils advertised as "synthetics", almost all the common ones you'd hear about are made up primarily of Group IV PAOs.

 

Their chain lengths, uniformity, and purity allow for excellent performance at both high and low temperatures. Additionally, they offer excellent worklife endurance, thermal and oxidative stability, and are particularly good at resisting water washout, which is an extremely important quality for guns.  

Wear in a bearing, stop-and-go traffic car wear, wear and tear stop and go

There are 5 broad categories of oil - groups I-III are refined, group IV synthetic, and V 'everything else'

The 'drawbacks' with PAOs largely depend on the intended application. Most notably, they offer little polarity, meaning they have little to no electrical charge to help their molecules adhere to the surface of a metal, meaning in part that they crawl a lot less on their own. However, this is an exceptionally important quality in PAOs, if you want to take advantage of boundary lubricants. Oils with high polarity not only crawl (again, a danger for cartridge primers but also in just thinning out in unsealed systems), but the greater the polarity, the more an oil will get underneath a boundary lubricant and keep it from doing its job. Interestingly, this lack of polarity in PAOs actually makes it difficult for them to accept additive packages to begin with.  

 

Tribologists get around this by mixing in smaller amounts of certain Group V oils - specifically esters - as the esters accept additive packages very well, and PAOs accept esters well. But proportions have to be very carefully balanced, as while the polarity of esters allows them to accept additives well, on their own they often accept it so well they won't let the boundary additives do their job.  So in putting together a lubricant based around the great qualities PAOs bring to the table, a quality tribologist will select the right ester, right down to the right ester molecule shape, to mix with PAOs to create the right balance of additives, polarity, thermal endurance, and stability in the presence of water.

 

The right synthetic blend can work with phenomenal excellence. But oil is oil - it is designed to flow, and will never achieve the ability of greases to endure and reduce friction in guns.