It sucked. We got them in early '67 and they started seizing up right away. They would tear the head of cartridge case off during extraction and then stuff a fresh cartridge into that. Crazy tough to clear and fatal if it happened in an intense firefight, which it often, often did. The Marines soon carried assembled cleaning rods, stuffed in a hole in the plastic forend so it could be cleared from the muzzle, like some throwback to the Civil War Springfield.
The sights were stupid - completely nonadjustable while you were using the rifle - and our Marines missed a lot because the rifles were hard to zero and windage was something you adjusted once while you were in the rear, maybe.
The safeties used to stick on Safe, the finish wore off almost as soon as you got them, the stocks were short and fragile and the rounds were often ineffective on the enemy; you could see the dust pop off them when you hit them squarely and they just kept running.
The enemy stuff never jammed - they did their R&D better than we did, apparently.
Thank you for your service. Did you get an upgraded replacement, or were you stuck with the same rifle for your whole tour?
“...The enemy stuff never jammed - they did their R&D better than we did, apparently.”
Not so concerning R&D.
The typical Kalashnikov functions reliably because it’s manufactured with very loose tolerances. Results in poor accuracy. Various tinkerers and machinists in the US have improved the accuracy, but the “improved” models always suffer loss of reliability. Which do you want - accuracy or reliability? Can’t have both.
The 5.56mm cartridge for the M16 was a result of infatuation in certain US Army circles with the SCHV (small caliber, high velocity) concept, which envisioned adequate lethality from low-weight bullets at elevated velocities. It promised to bring forth a rifle cartridge with greater effective range and lethality, compared to any full-caliber reduced-power round (such as 7.92x33 of the Third Reich, or 7.62x39 Soviet 043g).
Also dovetailed neatly with the US Army’s doctrine that firepower equaled shots per minute (USMC defines it as hits per minute). Since the 5.56mm round weighed half what a 7.62mm NATO did, each soldier could carry twice as much ammunition.
The SCHV theory wasn’t just smoke & mirrors: USSR started research into their own small-caliber round in the late 1950s, just as US 5.56mm development was ending. Resulted in the 5.45x39mm, adopted as Red Army standard in 1974 and still in use.
Initial M16 reliability problems came about from a combination of factors: sketchy operational testing (possibly compromised by US Army Ordnance officials who preferred the M14), refusal to chrome plate bore & chamber (USSR standard predating WWII, disliked by US Army Ordnance), claims that the rifle was self cleaning (always a poor idea when troops are involved), uncoordinated changes to propellant (unverified changes from chopped-tube to ball powder, use of calcium chloride as a drying/neutralizing agent in ball powder).
The United States Army had been the DoD executive agent for small arms, dating well back before WWI. Pretty much left any requirements out of the mix, for US Marines or the other armed service depts. Interservice competition and contention are never-ending.