Slamfire, have you even read through any gun magazines published since the early '90s? Just asking ... I haven't seen references to P.O. Ackley's work for well over twenty years now ...
I see I am going to have to save articles on Ackleyism and the gunwriters who use P.O. Ackley as foundational to their view of the world. I read the stuff, get outraged, and give away all my magazines, except Gun Tests. I just don't have space to keep decades of Shooting Times, Guns and Ammo, Guns, Handgunner, American Rifleman, Rifle and Handloader. Thankfully though, a few articles can be found on the web. Is 2011 within your twenty year span?:
Shooting Times
Coming of Age
by Layne Simpson | August 31st, 2011
http://www.shootingtimes.com/ammo/ammunition_st_age_200810/#ixzz4G5gmI8UW
Another benefit to improving a case—one discovered and written about decades ago by Ackley—is a reduction in backthrust on the bolt of a rifle during firing. Handloaders who use sticky bolt lift as a sign of excessive chamber pressures often don’t realize that it usually comes at a higher level of actual pressure with an improved case than with a standard case. In other words, if the .280 Rem. and .280 Improved are loaded to the point of sticky bolt lift and then their powder charges are decreased by the same amount for a safe usable load, chamber pressure is likely to remain higher in the improved case. So only by loading the .280 Improved to higher than recommended chamber pressures can velocities exceed those of the .280 Rem. by much more than 100 fps.
This is only eight months ago, my, my how short memory can be!
Shooter's Bible Guide to Handloading: A comprehensive Reference
Wayne van Zwoll 15 Dec 15
Ackley's scientific approach to testing cartridges, barrels, and actions set him apart. He carefully recorded test results, using them as empirical evidence to verify or trash longstanding assumptions. For example, to prove his points concerning case dign and bolt thrust, Ackley described tests with a Savage 99 and a Winchester 94. Creating a condition of grossly excesive headspace in the 94 action, he proved three major points:
1. Minimum case taper transfers more pressure to the chamber walls minimizing bolt thrust.
2. An oily chamber or cartridge increases bolt thrust.
3. While the chamber and bolt bottle much of the gas pressure, the case itself contains some.
I would like to comment on several of these points.
1. Minimum case taper transfers more pressure to the chamber walls minimizing bolt thrust.
Ackley never proved that. There was no instrumentation in Ackley's tests.
When you read his M1894 Ackley Improved test, Ackley starts off by claiming that no one knows the design limits of actions, which is a lie. What is certain he did not know, but that does not mean someone does not know. Designers are not going to provide that information to the general public, and it shows the limits of a skilled machinist when it comes to matters of mechanical engineering design. Ackley does not know, does not know how to calculate such things, does not know that increasing pressures above design limits reduces the fatigue life of parts, therefore he goes off in the direction if the action holds it for a couple of shots, the pressures must be safe.
P.O Ackley cartridges are very interesting and P.O’s test of a straight sided cartridge holding pressure without a breech block has been duplicated. The tester swabbed the chamber out with alcohol swabs between shots. The Ackley cartridge held. However the other cartridges, such as the 30-30, 35 Remington, blew out of the breech at 1900 fps. A 150 grain cartridge case flying at 1900 fps will go through both sides of most people's skulls.
Read carefully Boatright’s papers one of which he shows how a 308 case, in a clean chamber, can lock in and hold pressures by itself up to 25K psia.
Go to Jim Boatright’s web page.
http://www.thewellguidedbullet.com/
Look for yielding of the brass case in these studies
http://www.thewellguidedbullet.com/mechanical_studies.htm
However once pressures go above 25K psia, Boatwright shows the brass case stretches and if not supported, the case head will blow off.
Regardless of taper, cases are made out of brass and will stretch. There will be a bolt load reduction due to friction but it is inconsistent and not to be relied on in any way. Which is why breech mechanisms are designed to take the full thrust of the cartridge case, ignoring case friction, plus safety factors for fatigue life and manufacturing uncertainties.
Case friction is a real concern for the military as case friction causes problems. The first and foremost is that high enough case friction will cause failures to extract. You can look at calculations in the study “Analytic Study of Extraction Forces in the M16 Weapon”, Gordon, Frankford Arsenal Oct 1973.
If you notice, P.O. Ackley never printed experiments conducted with a 30-06 or a similar high pressure cartridge. I am certain if he had reported the results, it would have been a litany of case heads blowing out the back of his lug less rifles at lethal velocities. It is likely he did, given all the actions and barrels he had around, I believe it is more credible that he ran tests in a number of Ackley Improved cartridges but only published the test that supported his theory. We see this all the time when reputations and money are at stake. If he did not, then he should have bought a lottery ticket because he was very lucky. We do know that Ackley and others did not conduct sensitivity tests, varying chamber finish, (chrome for example), powders, primers, or much of anything else. There are axial loads which must be taken into account and case taper does nothing to reduce them, in fact his straight taper reamers reduce barrel thickness when used in a standard barrel. I totally disagree with the conclusion that Ackley and others have drawn, that his cartridges reduce bolt thrust and therefore a user can just pour the coal into the cartridge and let fly.
I like this guy's comments on Ackley's claims:
http://www.practicalmachinist.com/vb/gunsmithing/better-extraction-ackley-improved-247365/
Ackley cases are almost always horrible for extraction. Especially with firearms that have short extraction cams. Heavily tapered case's are always easier to get out. If you look at any of the old British cases designed for double rifles they always have a horrific body taper. This outwardly seams incredibly inefficient as you are wasting a lot of potential case space. The truth of the matter is that double rifles have little or no extraction power so they give them heavy tapers to get them out. Also the case only has to move 1/64th to 1/32 of an inch before it is completely free of the chamber walls allowing it to be tossed out by the spring loaded ejectors. If you can't grasp it, imagine a CAT40 and a #3MT quill. Which one is easier to get out of the machine. Same principal. There are people who believe that heavy tapered cases create more bolt thrust. In theory, if you use Einsteins theory's, NO, this would not be the case at all. The piston or cartridge head remains the same size no matter what the chamber is shaped like. In fact there is a slight variance as the cartridge case does obdurate and grip the chamber walls and contribute slightly to strength. This gain in strength is very marginal though and should not be used to add strength to the system. Its like arguing about how much padding you should wear before jumping out in front of a bus traveling 60 miles an hour. Who cares, its a stupid argument, give me an address I'll send flowers to the funeral
2. An oily chamber or cartridge increases bolt thrust.
I don't remember Ackley claiming he discovered this as this was well known to all gun designers prior to WW2. Such as Melvin Johnson:
Army Ordnance Oct 1936 What Price Automatic?, by Melvin M. Johnson, Jr.
Several methods have been devised to retard the unlocking of the block or bolt mechanically. The most appealing point in such a system is consolidation of the “automatic” parts in the breech. However, there is one serious difficulty. The conventional cartridge case does not lend itself to such a system unless adequate lubrication is provided, such as grease or wax or oil on the cases or in the chamber. Thus, the Schwarzlose machine gun has an automatic oil pump: the caliber 30 Thompson rifle (not the caliber 45 T.S.-M.G.) had oil pad in the magazine, and special “wax” was needed on the cases designed to be used in the Pedersen rifle.
And General Hatcher:
Army Ordnance Magazine, March-April 1933
Automatic Firearms, Mechanical Principles used in the various types, by J. S. Hatcher. Chief Smalls Arms Division Washington DC.
Retarded Blow-back Mechanism………………………..
There is one queer thing, however, that is common to almost all blow-back and retarded blow-back guns, and that is that there is a tendency to rupture the cartridges unless they are lubricated. This is because the moment the explosion occurs the thin front end of the cartridge case swells up from the internal pressure and tightly grips the walls of the chamber. Cartridge cases are made with a strong solid brass head a thick wall near the rear end, but the wall tapers in thickness until the front end is quiet thin so that it will expand under pressure of the explosion and seal the chamber against the escape of gas to the rear. When the gun is fired the thin front section expands as intended and tightly grips the walls of the chamber, while the thick rear portion does not expand enough to produce serious friction. The same pressure that operates to expand the walls of the case laterally, also pushes back with the force of fifty thousand pounds to the square inch on the head of the cartridge, and the whole cartridge being made of elastic brass stretches to the rear and , in effect, give the breech block a sharp blow with starts it backward. The front end of the cartridge being tightly held by the friction against the walls of the chamber, and the rear end being free to move back in this manner under the internal pressure, either one of two things will happen. In the first case, the breech block and the head of the cartridge may continue to move back, tearing the cartridge in two and leaving the front end tightly stuck in the chamber; or, if the breech block is sufficiently retarded so that it does not allow a very violent backward motion, the result may simply be that the breech block moves back a short distance and the jerk of the extractor on the cartridge case stops it, and the gun will not operate.
However this difficultly can be overcome entirely by lubricating the cartridges in some way. In the Schwarzlose machine gun there is a little pump installed in the mechanism which squirts a single drop of oil into the chamber each time the breech block goes back. In the Thompson Auto-rifle there are oil-soaked pads in the magazine which contains the cartridges. In the Pedersen semiautomatic rifle the lubrication is taken care of by coating the cartridges with a light film of wax.
Blish Principle….There is no doubt that this mechanism can be made to operate as described, provided the cartridge are lubricated, …. That this type of mechanism actually opens while there is still considerable pressure in the cartridge case is evident from the fact that the gun does not operate satisfactorily unless the cartridges are lubricated.
Thompson Sub-Machine Gun: … Owing to the low pressure involved in the pistol cartridge, it is not necessary to lubricate the case.
“Blow-Forward” Mechanism: We have seen above (blowback mechanism) that some method must be provided to hold the breech block against the barrel when the gun is fired, because otherwise the pressure of the powder gas pushing back on the cartridge case would drive the breech block back away from the barrel and let the cartridge out while the explosion was going on. With the blow-back gun the breech block is allowed to move in this manner, but is made heavy enough so that the movement does not occur too quickly.
Instead of allowing the breech block to move back, it would be quite possible to attach the stock and al the frame-work of the gun firmly to the breech block and then allow the barrel to move forward when the gun is fired instead of allowing the breech block to move back. Several automatic pistols, notably the Schwarzlose, have been constructed on this principle.
In 1917 an inventor appeared at Springfield Armory with a machine gun made to fire the Krag army cartridge, having the framework of the gun solidly fixed and the barrel loosely mounted so that it could move forward against the action of a spring when the gun was fired. This gun operated, but it was necessary to grease the cartridge case to prevent the front part of the case, expanded by the pressure, from sticking to the barrel as it moved forward.
One trouble with this system is that it greatly accentuates the recoil. The normal tendency of the explosion in the cartridge case is to push the bullet in one direction and the cartridge and breech block in the other. When there is no provision for locking the breech block to the barrel but instead it is attached to the framework and stock of the gun, and the barrel left loose, it is obvious that the explosion drives not only the breech block but the stock to which it is attached back against the shooter’s shoulder with a considerable amount of violence.
This inventor had besides his machine gun, a semiautomatic shoulder rifle built on this principle, though the mechanism was only crudely worked out. He demonstrated this gun by firing a number of shots with it and then allowed the Armory officials to fire it. I fired one or two shots with it and the kick was so terrific that I felt as though a mule had landed on of his hind feet on my shoulder. I seemed to be kicked back two or three feet from where I was standing and tears actually ran out of my eyes from the blow, which marvel as to how the inventor, who was a frail, pathetic looking man, managed to shoot it without any signs of discomfort. After showing his model he returned to a nearby factory to complete the mechanism but a few days later we were distressed to learn that he had taken his new gun and deliberately blown his head off with it. Probably the kick was too much for him after all.
3. While the chamber and bolt bottle much of the gas pressure, the case itself contains some.
Here is exposed a fundamental problem with Hatcherism and Ackleyism. Both assume the case is strong and the action is weak. Both also assume the purpose of the cartridge is to carry load, and protect the action from load. Nothing could be further from the truth. The action is strong, the case is weak. The action is there to protect the case. If the case carries load it will be stretched, deformed, and occasionally rupture. The action is there to carry all the load, the case is to carry none, or as little as possible. Friction between the case and chamber is undesirable for a number of reasons, difficult extraction one of them. Which is why trillions of oiled and lubricated cases were fired in military mechanisms. But all of the history I have repeated, it is over 8 months old. And based on the memories of those in this thread, they don't remember things from 8 months ago.
Twenty years ago a Clinton was President and soon a Clinton will again be President. Rip Van Winkle will wake up from his 20 year sleep and come to the conclusion, since Clinton is President, that it is still 1996!
