The push feeds of the '90's continued the same serial number sequence that started in 1936, with a "G" added in 1968.
100,000 in 1948. 500,000 in 1960. 1 million in 1970. 2 million around 1991. The first 873,000 (roughly) had no "G".
When the Classic came out they started over again at 1, but with a G in front. This run continued through 2002, at approximately G380000.
Starting in 2003 the "Classic" serial numbers were merged into the original, ongoing with the push feeds, serial run at around G2500000. Ending with the New Haven plant closure at around G3010000.
Damn confusing, but it looks like you have a handle on it.
I'm not 100% on this, but I recall that the "controlled round push feed" rifles were chambered for some specific short fat rounds. I remember reading somewhere was what they had to do to get them to feed. Why they wouldn't work as a straight push feed I do not know.
