Teddy12b;
Teddy, I have a 7400 and I have been using the Eagle 10 round clear mags in it for several years. They work as good as the factory mag, but, and this is a Big But, they do not have the charging handle release on them, and they do not hold the breech open when they are empty.
The charging handle on the 7400 is not very robust and just pulling it back and letting it go does not chamber a round for me all of the time using the 10 round mags. (I wish somebody would make a bigger replacement!) I get around this problem by chambering the first round using the release on the factory mag, then taking it out and putting the 10 round mag in. As long as I only shoot 10 rounds, i.e., leaving one chambered all the time, I can just insert the next 10 round mag and keep on shooting.
I have ten of them, got them from CDNNsports.com for $7 apiece several years ago. One time at the range I loaded up all 10 mags with Remington 150 gr FMJ and began shooting. I shot seven full mags without a misfeed and then stopped because the barrel was getting quite hot! So, my experience with them was pretty good despite the drawbacks I mentioned. One plus is that the mags are clear and are numbered for the rounds, so if you loose count you can see the mag getting empty.
BTW, my 7400 is no tack driver, but it will put them in a 4" circle at 100 yards. It is topped with an early Simmons Aztec scope, one of the good ones, I guess.
Sincerely, Kanilure