The Kalashnikov had been designed in 1947, (hence, AK-47), but it took more than a decade before a bug-free version (the AKM) was considered reliable enough to make standard-issue. (When this article refers to "AK-47s", most of the actual weapons involved were actually AKMs.)
The US, by contrast, had spent the decades since WWII resisting the assault rifle concept, so that when Vietnam rolled around their fantastically rich and well-funded military found its infantry outgunned by peasant militias wielding second-hand Soviet rifles. So the rifle went from initial acceptance, including these kinds of stupid last-minute design changes that are common in any project, to large-scale combat deployment within a year; normally, there would have been years of incremental usage to catch these bugs, but the rifle was so desperately needed that it was rushed to the front.
A book I've recommended in another thread, which gives a great introduction to the history and impact of the Kalashnikov in particular and assault rifles in general, is C.J. Chivers's "The Gun" (https://www.amazon.com/Gun-C-J-Chivers/dp/0743271734), or this shorter-form article he wrote in response to recent msas shootings (https://www.nytimes.com/interactive/2016/world/ak-47-mass-sh...)
I read it not so much as a historical text but as a story about dramatic shifts in power attributed to technological advancement and strategy.
- The original cartridge (.223 caliber) that the AR-15 was based on was designed for shooting "varmints" (small- to medium-sized furry mammals): In Vietnam it was found that the M-16 tended to wound rather than kill the enemy, and a new doctrine was adopted to suit this fact. In contrast the AK-47 cartridge (7.62x39) was designed to _kill_ large hairless mammals (men) and does so with dispatch.
- In Vietnam the M-16s (AR-15) jammed all the time. To unjam one you had to put a stick down the barrel and dislodge the jammed round, not an easy task when you're lying on your back and VC are shooting at you with ultra-reliable AK-47s. The M-16 is one of the reasons we lost that war. C. J. Chivers writes about the sordid history of the M-16's development and deployment in his book "The Gun" (link below)
I have often joked that the US government _wants_ their citizens to buy AR-15s because an AR-15-equipped citizenry is effectively disarmed.
I was astonished to hear that the Orlando shooter had an "AR-15" since those are usually "Jam-O-Matics". My astonishment vanished when it was revealed that the shooter used a Sig Sauer MCX, which has a better design and does not jam.
You can read an excerpt from "The Gun" at Esquire's site:
And here's Mikhail Kalashnikov's 2006 take on the M-16 vs AK in Vietnam and other wars:
The Author, C.J. Chivers, writes an interesting blog for the NY Times where they attempt to ID munitions from the battlefield in Africa, Syria, etc. http://cjchivers.com/
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