I agree with you - except that, by your basic criteria, the "most successful western infantry weapon ever produced" was the American-designed Lee-Enfield bolt-action rifle. It served SIXTY PLUS YEARS (not a mere "FORTY" ;>) as the primary infantry weapon of a major western power, and 'DOMINATED' the target-shooting and law-enforcement markets of the British Commonwealth (and IIRC, the population of the Commonwealth exceeded that of the US during that period ;>).
And lest we forget that this is primarily a discussion of ammunition (rather than firearms - many of the folks here would apparently love the M-16 if it just chambered a round with a little more 'authority' ;>), one respected ammunition reference has noted that "it is doubtful that any other military cartridge has been used in so many hostile encounters as the 303 [British]." So much for "the most successful western infantry weapon ever produced"...
By the way, I love these threads - comparing firearms apples with ammunition oranges is always entertaining (and frequently informative)...
;>)
OK, most successful western self loading rifle. And my criteria is actually production volume, only the AKM has been manufactured in greater quantity - again excluding bolt guns that have been in and out of production for 100 years.
The kicker is that the M16 has been in service as the primary US infantry arm longer than any other rifle.
Not bad for a "crappy" rifle in a "varmint" cartridge.
It had a 60 year head start. I'd also expect 762x39 to be all alone out front in terms of sheer volume of hostile fire, after 50 years of pretty much nonstop use worldwide.