I just bought a mec 3 1/2" steel master reloader from a friend for 50 bucks and was wondering just how many shells will 7 lbs of shot load any one know???

Allen,
It depends on how much shot you are putting in each round. 7 pounds has 112 ounces and at 1 ounce (not enough) you would have 112 rounds. I will let you do the math on the load you want.

BTW, welcome to AR.