I thought the Remington mag goes back to 1960 and they're still selling rifles (auto and pump) that still utilize those mags. That's more like 60 years, but then I'm nitpicking. You're right the 742 itself stopped production in the 80's. I still say it's a crappy magazine design.
Shaman
You are pretty close in thinking 1960. First year of production of the M760 was 1952. According to Eugene Myszkowski, who authored a book on Remington pumps and semiautos, there have been 9 versions of M760/7600 magazines. Unfortunately, all versions are the same design in how they are latched in the receiver though.
IME, great care needs to be paid in inserting the magazine into the magazine well in order to not get an unintentional mag release. Correct insertion is helped if the magazine is tuned and they all seem to need it now and then after some use. Although I have tuned a few magazines, it does not get easier. It is a tedious process of nudging the sides of the magazine so that it will slide into the magazine well without hanging up anywhere . This allows feeling the 'click' as the spring loaded latch drops into the locking lugs at the back of the magazine. Next, by tugging on the magazine, I can check if the lug at the front of the magazine is engaged in it's mortice. Doing this, I've reduced the events of unintentional magazine drops considerably.
Yeah, it is a crappy design.
