The attached link might show something about lubrication affecting bolt face load or bolt thrust, force as measured in pounds.
www.dtic.mil/ndia/2011/ballistics/11826.pdf
The primary reason these Army coverups work, is because no matter how incompetent the Army Ordinance Bureau might be, the general shooting community is much more incompetent and extremely gullible.
What the Army did was cook both the SAWS and its ammunition at 160 F and they shot the stuff at that temperature. This temperature, 160 F, is their maximum storage temperature. Their maximum operational temperature is 125 F, but needless to say, the Army was cooking the weapon and the ammunition at 160 F and testing it in an operational configuration and had malfunctions. You can look at their data and their computer modeling predicted pressures around 70,000 psia. I suspect actual pressures were closer to 90,000 psia. Regardless, 70,000 psia is the pressure of their old 5.56 proof cartridge, and they were firing proof pressure level cartridges in their test and were surprised that they had malfunctions. You can see from all the charts and stuff, it is apparent the Army did not know that heating ammunition raises combustion temperatures. Instead of acknowledging this, the Army blamed oil for their problems! Claimed that oil dangerously raised bolt thrust, and basically ignored all the problems they created by cooking their ammunition.
Specifications are very important. Operate equipment beyond specifications and things will fail. Apparently the Army Ordnance Corp does not even know the specifications to its own ammunition and small arms. It is mind boggling that they are testing their ammunition beyond their own specifications. They really don't know that their ammunition is only spec'd to 125 F.
From the report:
During a U.S. Army test, 5.56mm NATO case ruptures were experienced when firing the M249 in the hot, 160 deg °F (conditioned) environment.
It used to be that ground equipment met a -40 °F to 125 °F operational temperature environment. That temperature range for ground based equipment goes back decades, and it worked extremely well. Storage temperatures were higher, typically 150 °F to 160 °F . This difference is critical to understanding what they were doing and why they had an equipment failure.
Mil Std 810 G is the primary source for Army environmental requirements. This document is the first place to go to see what climatic and environmental conditions Army weapons are to be designed to meet, and how they will be tested. This stuff is out there on the web, anyone can look it up, and follow the logic and rationale. Table C-I.
Summary of climatic conditions and daily cycles of temperature, solar radiation, and relative humidity shows the highest operational temperatures expected of a weapon system in a hot/dry climate to be 120 °F . The highest storage temperatures are 160 °F , at which the weapon system is either stored, in transit, but not being used. I would consider shooting a machine gun to be an operational event, not a storage event.
Incidentally, a little reflection on what 160 °F means, if anyone thought about it, to a human handling a 160 °F weapon. My Rheem water heater came with this
warning: "Water temperature over 125 °F can cause severe burns instantly or death from scalds." It takes one second or less for 155 °F water to cause a scalding burn. Coffee come out of my coffee maker at 170 °F and I have to wait till it cools down before I can drink it. A 160 °F weapon would be too hot to handle. Does the Army issue oven mitts with each M249?. So why test the thing, and its ammunition at 160 °F ? From my spec research, they were not following their own requiring documents, the 160 °F hot dry requirement applies to non operational equipment, but they had conditioned the weapon and the ammunition to 160 °F and were firing the combination at this temperature. This temperature range is also out side of the range for human survivability and therefore, ignoring any requirement documents, it does not make sense to have an operational test at this temperature.
Now I am going to challenge everyone reading this to do what I did, and what the Army Ordnance Bureau did not, and that is go through every 5.56 ball ammunition specification and look at the maximum operational temperature requirements for the various 5.56 mm cartridges. Not one ammunition specification or propellant specification has a 160 °F operational requirement. Not one. Pressures are not controlled for ammunition fired at temperatures above 125 °F . The Army is shooting their cartridges at temperatures where the pressures can be anything, because 160 °F is beyond the cartridge specifications.
MILITARY SPECIFICATION 63989 Cartridge, 5.56MM,BALL, M855
3.7 Chamber pressure. The average chamber pressure of the
sample cartridges, conditioned at 70 + 2°F shall not exceed
55,000 psi. Neither the chamber pressure of an individual sample
test cartridge or the average chamber pressure plus three standard
deviations of chamber pressure shall exceed 61,000.
temperature extreme specified below shall be in accordance with the following requirements.
a. Conditioned at 125° + 2°F for not less than one hour and fired at that temperature.
b. Conditioned
3.10 Temperature stability. The action time, pressure and velocity of sample cartridges conditioned and fired at the at -65° + 2°F for not less than one hour and fired at that temperature
3.10.2 Chamber pressure. The average chamber pressure shall not vary from the average chamber pressure of the sample test cartridges conditioned to 70 + 2°F by more than 5,000 psi.
Any decrease in chamber pressure is acceptable.
Mil-P-3984J Military Specification, Propellants for Small Arms Ammunition.
3.2.11.2 Cartridge 5.56MM. The average velocity and average chamber and port pressure of test cartridges subjected to the following storage conditions shall not vary from the average velocity and average chamber and port pressure of similar test cartridges conditioned and fired at 70 ± 2 degrees F by more than the following indicated amounts.
Condition : Stored at 125 ± 2 degrees F fr not less than one hour at that temperature
Variation in Variation in average velocity: -250 fps
Variation in average chamber pressure: + 5000, 6,500 psia for M855 and M856
Variation in average port pressure: : ± 2,000 psia
I think this 2010 incident, and subsequent cover up, made Army contractors realize that they need to educate their Government counterparts about the limits of the products they are buying. If you go through this 2017 ammo book, note that each page reiterates what should be common knowledge, the ammunition has a 125 °F maximum operational temperature range. I suspect Orbital is hoping by repetition of this information, they won't have to field complaints from the Army Ordnance Bureau about malfunctions caused when their ammunition is heated up to 160 °F, or 212 °F, or 500 °F, or the temperature of the sun.
Small Caliber Ammo Book
http://www.orbitalatk.com/defense-systems/small-caliber-systems/overview/docs/Small Caliber Ammo Book 2017.pdf
To anticipate an argument, if you don't like the environmental ranges specified in Mil Std 810, maybe you are one of those who thinks Army equipment and ammunition should operate on the surface of the sun, let me out line a path forward so you can change these requirements to your satisfaction. Become a four star General and be the Army Chief of Staff. As the head of the Army, you can dictate to your subordinates. Or, become President of the United States and dictate the high temperature operational requirement to your Army Chief of Staff. All other alternatives , such as complaining that the requirements are un realistic, and demanding change, will come to naught.
So when the Army cooked their ammunition to 160 °F , pressures climbed. As noted earlier, their ammunition has to meet a 125 °F pressure limit, which is still very high, but since these ammunition specifications are in fact, legal, contractual documents, ammunition fired above 125 °F can be of infinite pressure, and the ammunition manufacturer is not liable for any reason. I really wonder if it is physically possible to make gunpowder which could stay within the M16 pressure requirements from -40 F to 160 °F . The gunpowder has to function the gun at -40 °F and meet function requirements, and not exceed the action limits at higher temperatures, and meet function requirements. I really believe the Army has lost its core technical competency, does not know this fact any more, and is clueless about what happens when ammunition is heated. For those who are intellectually qualified to be Army Ordnance Bureau employees, it is a fact that pressures increase when gunpowder is heated. You can see this documented at this web page.
The Effect of Temperature on Ammunition Performance http://firearmshistory.blogspot.com/2012/11/the-effect-of-temperature-on-ammunition.html. Just by reading that page, you are now over qualified to be an Army Ordnance Bureau employee!
Their study is such a sham. The numbers are true, break the friction between case and chamber and bolt thrust goes up. So what, firearms are designed to carry the full thrust of the cartridge, but within limits. I don't think they know this and it is so easy to calculate. Bolt thrust is based on the OD of the cartridge and a maximum chamber pressure. The Army raised chamber pressures to 70,000 psia and beyond, and bolt thrust went up too. At pressures above proof pressure, the case head balloons and ruptures. If you notice, they sort of ignored the temperature part of the pressure problem, instead, the Army blames all of their problems on oil. I am going to say slick cases are the least of their problems when their cartridges are operating at 90,000 + psia. They also don't know the load limits of the action they are testing. This presentation does not have a fundamental number: What is the design load of the bolt? This, along with the baseline procurement environments, should be all over this presentation. It is not. The Army should know the requirements it bought the weapons against, but they don't. I think they forgot. It is clear, the Army does not know the loads that either Stoner or FN used in designing their locking mechanism. The Army did not design either weapon, and apparently, does not even know what the requirements are for either weapon. I will bet, neither weapon was designed to continuously fire ammunition at or above proof pressures.
I don’t know how the M249 would have functioned in 125 °F temperatures dry or wet, but one thing is for certain, the Army must have been testing the M16 at 125 °F and 160 °F and was not having issues. But this would have been serendipity. I believe this is an incident of monkey see and monkey do. I suspect the test guys got the bright idea to save money on the M249 program by combining the high temperature operational test and the high temperature non operational test. But the M249 is an entirely different mechanism with a different bolt design. One that would meet spec, but one that was not as stiff as the Stoner bolt. I think the monkey's in charge did not have any inherent understanding of why they should not have run an operational test at 160 °F, and out of ignorance, they went out and ran the test. Since it was beyond the specifications of the ammunition and the weapon, the M249 failed. This study shows they still don't understand why their machine gun choked. It is apparent the Army Ordnance Bureau has no idea about the operating parameters of their own weapons, their own requirements, nor the effects of temperature on ammunition.
This study is another Army cover up of Army incompetence. And once again, poor defenseless oil is being blamed for a problem that the Army Ordnance Bureau created.
