I just read somewhere that not removing case lube from cases causes the case to move / slide backward during firing and putting undue stress on bolt faces. That the case should be dry (all case lube removed) to grip the cylinder / chamber wall.
This is an Army coverup of their defective low number M1903's, and is over 100 years old. The Army built over one million M1903's in Arsenals without temperature gauges, and based on their own (1927) tests over one third were structurally deficient. Steels were being heat treated by eye and it is very easy to burn steel, just watch Forged in Fire. The knife smiths on that show are pressed for time and there is hardly a show which a knife, sword, does not fail by being too brittle. Rarely they fail by being too soft. Heat treatment is very tricky.
At the same time competitors were greasing bullets to reduce jacket fouling. I purchased 303 Iraqi ball with cupro nickel jackets, which were the same jackets of the early 20th century, and the jacket fouling was unbelievable. Sections of the bore accumulated lumpy fouling that just built up and the stuff was extremely hard to remove. The chemical formulas of the day often ruined the barrel. However, a thick coating of grease positively prevented jacket fouling.
Understand the Army is no different from any other large organization. All large organizations are grandiose, self centered, have no empathy, and are totally focused on their needs. They follow the vile maximum:
All for me and nothing for anyone else. To accomplish this they become very manipulative, and they never ever admit fault. They scapegoat and create nonsensical explanations to shift the blame. You can only have a master/slave relationship with them. If you are negotiating, they know you are weak. They have all the personality characteristics of human psychopaths.
https://www.healthline.com/health/psychopath#signs
https://www.psychologytoday.com/us/basics/psychopathy
So, you can see the logic. Perfect Army rifles blowing up with perfect Army ammunition, so the fault has to be the grease, right?
What has kept this coverup going is generations of in print gunwriters who repeat the Army coverup. It really shows their lack of expertise as they are totally ignorant of the hundreds of models of semi automatic rifles, machine guns, and machine cannon that used greased and oiled ammunition. These guys parrot what the Army taught them and if saw the historical weapons, never considered the contradiction between their belief system and what was in front of their faces. Based on what I have read, they are largely unaware of these mechanisms. They don't know firearm history. But then, what do you expect from shills? These guys are picked for their ability to work cheap, pump product, and create sales, not for their understanding of firearm history nor mechanical engineering.
Now, of course grease and oil increase bolt thrust. So does firing a round in the chamber. The question I ask of Hatcherites and Ackleyites is "
how would you design an action?" and more specifically,
by how much would you weaken the locking mechanism based on the assumption the case carries load. ? This is an incomprehensible question to these guys. Like asking a fish for a pin number. I believe that Hatcherites and Ackleyites view rifle actions as things that have "grown". They can drive down the street, trees on the left, buildings on the right, and they genuinely believe that the buildings, like the trees, have all grown from the ground, and that benevolent God gave both all the structure necessary to stand. And of course, rifle actions have grown, or been born, with all the structure necessary to support a cartridge and any idea that the buildings, bridges, rifle actions, were designed to a load, does not occur to a Hatcherite.
This is how Lilja sizes a rifle bolt:
A Look at Bolt Lug Strength
He uses the simple shear failure model, used ID of the case (I think OD is a better width), and applies a two to one safety factor to allow for the vagaries of metal composition, mechanical fitting, and heat treatment variation. With a two to one safety factor the designer hopes the mechanism will have a lifetime of one given a load of one. Ignorant people assume a 2:1 safety factor means the action is twice as strong as needed. Well, maybe a perfect action, built out of perfect materials, machined and heat treated perfectly. A new perfect action should hold up to excessive pressure for a while. But add some use, metal fatigue, a structure that might have with stood a 2:1 load when new will break with a load just over 1.0.Given lots of time and use, the structure will break with a load less than one. We have all experienced this. I have twisted the heads of 47 year old bolts that corrosion, wear, and time weakened. And for you geezers, remember when you could pick up a refrigerator all by yourself?. Now, if you try something stupid like that, your back will give out. Age is not nice to anything.
As long as you are firing SAMMI spec spec ammunition, a light coating of grease or oil is not going to ruin the action. Over pressure ammunition is bad, it over stresses the locking mechanism and will reduce the amount of rounds till the lugs crack. Lugs do crack, light weight rifles were never built to last forever. A lifetime of AR15 bolts was in a thread from AR15.com, and I lost the reference. But what I remember, some shooters, their AR15 cracked a lug at the low end of 10,000 rounds, some of the better built bolts were going to 30,000 rounds. Few shooters ever shoot a 1000 rounds through their rifles so lug cracking is very uncommon, but some of the AR shooters are very high volume shooters and they will learn to buy bolts when they are on sale.
Incidentally steel case ammunition is lubricated, in various ways, to keep the stuff from sticking in the chamber. Wolf developed a sintered Teflon coating and applied it to their steel case ammunition. This is what Wolf used to say:
Superior Reliability: The application of the polymer creates a precision uniform coating around the casing. It produces a bullet with persistent, uncompromising, stable dimensions thus leading to smooth reliable extractions.
Better Functioning: The superior lubricity improvement eases wear in gun chambers and alleviates excessive operational and maintenance issues associated with rapid firing. The development of this polymer represents a break-through in the field of tribology, and incorporates the most recent chemistry in terms of lubricity improving molecules.
This is what they say now:
Polyformance ammunition will not disappoint! Wolf coats all of their ammunition with a polymer coating to ensure smooth feeding and extraction putting the shooters mind at ease with less jamming. The coating on the ammunition allows for the ammunition to have a lengthier long term shortage time in comparison to different manufacturers
Notice that Wolf now calls the stuff a
polymer and has stopped calling it a
lubricant. I am certain they have stopped alluding to Polyformance as a lubricant because the the extreme reaction they got from Hatcherites who howled that lubricants will "
increase bolt thrust". But, Hatcherites have real limitations:. Firstly to them, lubrication is not a principle, lubrication is greases and oils. For example, they don't recognize the wax coating that Pedersen put on his cartridges as a lubricant, because to them, lubrication is greases and oils. Waxes are not greases and oils. Therefore to a Hatcherite, coating a case with teflon does not increase bolt thrust because telfon is not a grease or oil and therefore is not a lubricant. Hatcherities also don't know that oil, grease, wax and teflon are all polymers. Calling a dry film lubricant a polymer, instead of a lubricant, won't cause angry reactions from Hatcherites. They can't make the connection.And I am certain instead of dealing with medievally ignorant Hatcherites, Wolf simply changed the terms to make them go away.
Aluminum case ammunition has a number of coatings, one of them is wax. The wax aids in extraction of aluminum cases, but this is not advertised because ammunition manufacturers expect irrational reactions from Hatcherites. Why stir up the animals?
But my question is on how pressure is gauged by some on the degree of flattening of the primer. It would seem then the degree of primer flattening would somewhat depend on whether the case "slipped" back to some degree or not.
So is gauging pressure by the degree of primer flattening a reliable indicator of pressure?
I don't know much about the above so just throwing this out to see what others think about this.
I found that the primers on my M1a ammunition went from flat to rounded once I started lubricating the ammunition. Friction between the case and chamber held the case in place, as pressure built up, but the primer backs out on ignition. Rarely you will encounter fired ammunition with backed out primers, such as what happened to me :
Adhesion between case and chamber was strong, and internal pressures plus the force holding the primer out, was such to prevent stretching of the case sidewalls. Obviously this is a relatively low pressure load.
James A. Boatright addresses case wall stretch in his
Yielding of Brass Case Walls in the Chamber. Professor Boatright uses a brass yield strength, at the case head, of 59,200 psia. This is extremely hard brass, and too hard for the case neck. I don't know how Professor Boatright came up with this number, the Army number I read in AMCP Pamphlets was quarter hard brass, 44,000 psia. Regardless, Professor Boatright, in his calculations, used 59,200 pounds per square inch for the yield strength of brass in the case head area. He claims the case head does not expand into the chamber, and it is at this location where the sidewalls stretch to the bolt face.
Now the important thing to understand about Professor Boatright's calculation is that while ultra hard brass may have a yield strength of 59,200 psia, but cartridge cases are not one inch thick! Based on his estimate where case heads stretch, the case wall thickness is 0.045 inches.
So, given case sidewall thickness of 0.045 inches, you would expect the case head sidewalls start to stretch given an internal case pressure of 25,000 psia. This assumes good adhesion between case and chamber, and assumes there is room for the case to stretch. A "interference fit case", that is a necked sized, or partially necked size case which is an exact fit to the chamber, will not stretch. The case sidewalls have to stretch to reduce bolt thrust, no sidewall stretch, no bolt thrust reduction. So the practice of neck sizing and partial neck sizing imparts the full bolt thrust to the case, similar to the thrust of a lubricated case.
So, if the case has good adherence to the chamber walls, the primer backs out, the case sticks to the chamber walls up to the pressure point that the case sidewalls stretch, and then the primer is stuffed back into the primer pocket. Since this is usually around 20,000 + psia, the primer has expanded and looks flat once stuffed back into the case primer pocket. This gives a false reading of excessive pressure. It is particularly bad with gas guns.
Anyway, once I figured out that lubricated 308 Win cases gave rounded primers in my M1a, whereas dry cases gave flat primers, for the exact same loads, I decided to conduct my load development with lubricated cases. With a lubricated case the whole case slides to the bolt face, stuffing the primer in the pocket before internal pressures expand the primer. With lubricated cases I often see a transition from rounded primers to flat primers. Usually at that charge level, I am at, or have exceeded maximum pressures. But it is most unreliable. Loads developed with case lubrication, showing round primers, have blown the primers or pierced the primers later. I do develop loads with lubricated cases, one reason fire forming new cases with a lubricant, results in a perfectly fire formed, stress free case. I don't get any sidewall stretch, and these 300 H&H cases are $2.00 each. I want them to last. First firing, I lubricate them.
The second reason is I want to see the transition from rounded primers to flat primers. When I am there, I know pressures are pretty high. I don't know how high. And with one 270 Win, very high pressures did not register with lubricated cases. I only figured out the pressures were too high when I primed the cases later and found the pockets had expanded. A lot. Primers give unreliable indications of pressure. Might as well read tea leaves.
I am going to claim the only real physical indications of excessive pressure are sticky extraction, blown primers, leaking primers, and expanded primer pockets. And the pressure level that creates these indications are way above any "safe" pressure for the case and action.
The more you shoot, the more load cutting you will do. Just when you think you have a safe load, something bad happens, and you have to cut the load more.
As an example, this load just seemed great. Fast, accurate, shot plenty at 100 yards.
took the rifle to CMP Talladega to get a 600 yard zero, and what do you know, excessive pressure.
I am going to cut the load to 57 grains of AA4350, that will give a velocity around 2700 fps, and as long as it does not etch the block face and dish the primer, life will be good.
