If you want honest chronological info about the cartridges history, AND the weapons it fires in; try this:
http://www.thegunzone.com/556dw.html
Here are some of the highlights from this source, in rebuttal to your claims.
1 - Maybe, however the headspace is NOT longer; the leade is longer. The original chamber had the exact same throat, read about the meeting with Remington below. It also had a 14 twist, then 12 twist, and then.... you get the idea.
In fact American Rifleman wrote an article on the AR15 in May 1962, proposing that they changed from the 14 TO the 12 twist. They had a brief over-winter test that showed poor bullet stability. During congressional hearing during that month, the USAF was asked to rebuke that magazine article. McNamera signed off on the change to a 12-twist in July '63.
2 & 3 - The "testing phase" was was so long, which powder do you mean? April 63 they were using IMR-4475.
Secretary Vance submitted a memo to McNamera, titled "Standardization and Procurement of the AR-15 Rifle" in which was specifically stated that ammo should be procured competitively from commercial sources.
Sept. '63 - Cartridge, 5.56mm Ball, M193 was officially type-classified. It spec'd a Rem designed bullet @ 3250 fps with IMR-4475 to 52,000 psi. Ohlin complained about that powder and some case specs. Rem also about the case, and wanted to bump the pressure limit by 1K. Federal wanted an extra 1K psi above Rem.
Dec. 63 The USAF gets lots of ammo with WC846, which is your claim. 846's usage had nothing to do with fill volume. It had to do with it being already available, and meeting the spec, period. Unfortunately in Frankford's 8th memo, the one outlining the "fouling issues" came from commercial lots of IMR-4475...OOppps. The primers ultimately came into question for containing Antimony Sulfide, and Calcium cillicide.
Jan. '64 - the big 3(Ohlin, Rem, Federal) met with the army to talk powder and pressures. Rem claimed the army mis-read the original print, so the chamber was THEN changed. There is also a pressure waiver for M193 ammo. THAT is where the individual cartridge pressure of 60,000psi came from; NOT the average operating pressure. Under that waiver a million rounds were authorized. Testing was ALSO done with: CR-8136, HPC-10.
April 64' Both CR-8136 & WC-846 are authorized for use. In 65 so was EX-8208-4, and later 8208M.
Sept. 64 - Frankford did a study on the case specs. That was completed in October. No metalurgical controls or changes were deemed needed.
4 - That nifty glued strain gauge is a very well established, and accurate system. If you read the article referenced, the author consulted ammo manufacturers about his method; and was told it was sound.
5 - Probably so does your thermometer, neither of which is concerning the issue, nor helpful to it.
I'm glad your book was entertaining to you, but it doesn't seem to be the complete history of the cartridge and weapon systems.
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