The AR15 was designed on a shoe string budget but the Military Industrial Complex got the Department of Defense
"a little pregnant" and a lot of good American boys died in Vietnam with jammed M16's in their hand. There are a number of books on the subject, quite literally the Army Ordnance Bureau spent hundreds of millions fixing tiny problems, with the weapon in combat, but there are limits as to what can be modified when a system is baselined, in production at a contractor's facility . A contractor who incidentally owns the technical data package, and will charge the procuring organization for hundreds of millions of dollars if it is told to make changes to the hardware. These for profit organizations know the Department of Defense has a bottomless bank account, and they charge accordingly whenever they can. So, the Army made little changes here and there, chromed chambers, better rust resistance, etc. Magazines remained a major source of unreliability till polymer technology (Pmag) was mature enough to create an exact form, fit, and function part out of a more durable material. And that was more than 50 years later.
The AR15 always had, and still does, have an extractor lift issue. The extractor will come off the rim, the round falls off the bolt face causing a jam.
Understanding Extractor Lift in the M16 Family of Weapons
https://slidetodoc.com/understanding-extractor-lift-in-the-m-16-family/
You can see in the presentation, researchers had to grease the cases to keep them on the bolt face.
I believe this is due to two factors, Stoner did not have the budget to do a time, movement, pressure curve test. And, he used a cartridge that was a wildcat.
The 223 round was not so much “designed” as it was a wildcat. The guys who came up with the round wanted a certain velocity at a certain range. I read the 1971 Guns & Ammo article
“The 223 is here to stay” by Robert Hutton. Robert Hutton was technical editor of Guns and Ammo magazine and must have been very wealthy as he owned a big piece of real estate in Topanga Canyon California. It was called Hutton’s Shooting Ranch.
Hutton’s article documents how he developed the 223 round. If you have any sort of technical background, it is apparent he is an amateur and his cartridge represents what an amateur would do. He took an existing cartridge, necked it up and down, blew the shoulder out, changed shoulder angles, he had a chronograph, got the velocity he wanted at distance. The crowning achievement in the article was punching holes in the wobble pot helmet at 500 yards. That is about all the lethality testing Hutton did, punching holes in a helmet. He used the Powell Computer, a paper slide rule, to estimate pressures. He did not pressure test his cartridge. He used the powders he could buy at the Gun store. This cartridge was then adopted as the US service round.
I have no idea of his background obviously he was a firearm enthusiast, and being the Technical Editor of a Gun magazine made him well connected. Unfortunately, amateurs don’t have the time, equipment, or understanding to really sweat out the tiny details. These guys did not have the analytical capability nor probably, had the comprehension to thoroughly study cartridge case design. William Davis, the Government Technical Expert at the Icord hearings, said on the History Channel that the technical data provided the Government on the 223 round
did not come with a pressure curve. Hutton created a wildcat never thought of documenting what the pressure curve looked like. Pressure curve is absolutely critical to the timing of an automatic weapon. How long energy is available, the maximum pressure and how fast it drops off is fundamental to the design of a automatic gas mechanism.
This is from Chinn's Machine Gun series.
View attachment 1016933
Hutton did not look at case hardness, taper, expansion or contraction. A professional would have looked at the expansion and contraction of the case in the chamber and adjusted case taper, thickness, and established case hardness in the sidewalls and case head. You would expect the cartridge design team to consult with manufacturing to determine realistic hardness parameters throughout the case. This is important as it affects the Young’s Modulus. As it turns out, the brass case 223 drags on extraction, there is not enough clearance between the case and chamber. Steel case is even worse. I have seen many failures to extract steel case ammunition on the firing line with AR15’s.
Then there were other issues, one of which, when the pressure curve was measured, manufacturing technology of the era, could not hold the tolerances. As a made up example, the powder manufacturer made ten lots, following best practices, and then went out and tested which lots met cartridge pressure curve requirements. Lets say, five lot passed. The Army received those five lots, at their cartridge factory, and was charged for all ten! The Army did not did not like charged for ten lots when they always received less, and told the powder manufacturer to "qualify", that is guarantee, that all lots made by the powder manufacturer met requirements. Given that ultimatum, the powder manufacturer told the Army to go pound sand, and the Army lost its powder supplier! And that was the origin of the stick powder versus ball powder problems of the era. The Army used M14 ball powder in the 5.56 case and that caused a lot of failures to eject.
Because Hutton had no idea of the brass hardness levels in the case needed for function, the Army had to figure that out with the weapon in combat. And the best they could do, altering case hardness and thickness, it ends up the 5.56 case still drags with brass as a case material. Unfortunately for the user, the unreliability level is considered acceptable by the money men. Which, I am sure, is no comfort for the guy whose gun jams in a hairy situation. However, the cartridge performs even worse with steel as a case material.
From the very beginning, the 5.56 cartridge was a poor design, the weapon and accessories finicky, a total example of what happens when a “
not ready for prime time gun and cartridge” gets introduced and issued as a Military weapon.
So, if you are seeing that the AR is pulling on the rim, with different AR’s built by different makers, all pull differently, that is the nature of a kludge design, made of cobbled together parts, and sent out with a wish and a prayer that it works longer than the warranty period.
I don’t read Russian, and don’t have access to the Russian Defense Technical Reports website, assuming there is one. So I don’t know why AK’s are showing extractor marks. The AK and its round were properly designed, a short case with a lot of taper, and designed for the very start to be made from steel. I have never shot my AK enough to really stress the thing, but did you know, military capture AK’s were tested by the Air Force against M1 carbines, M1 Garands, and M14’s, and Stoner’s AR15, and the reliability of battlefield capture AK’s were better than the AR15. I forget how it placed against the other weapons, but it was pretty darn good. At the time, the Soviets were not selling AK47’s to our military. We were sort of not best buddies at the time.
Not disagreeing, I don’t know all weapons, but I don’t know of a weapon out there that will extract and eject without an extractor. The case will fall off the bolt face. I am sure there are designs that require the extractor to pull the case out of the chamber, and I am also sure, extractor lifetime is short in those mechanisms. The AR is not the only kludge on the market. Why don’t we talk about software, and how software developers always create error free software that never requires patches?
, no misfires or malfunctions, and accuracy has been fine. Just the other day I ran a box through my older Sig P226, and was quite happy. I'd got some "used in fair condition" magazines for a decent price, these ran through a couple without any problems. I used the ammo box at 15 yds as a target, and kept every rd on paper. When you consider that's the size of a pack of cigarettes or an iPhone, shooting casually from a standing position with no bracing, I'd say the ammo did just fine. I've also shot it through other guns, and again no problems. I picked up a 2nd Star Modelo Super (got both the Largo and Luger barrels), and used some of the Largo mags- fed fine. More reliable and consistent than, say, old Remington UMC. 
