A standard capacity mag of 15 rnds (which became a high capacity mag with the passage of the 94 AWB), made before the signing into law of the AWB, was was totally unrestricted by the AWB.
Mags made after enactment of the AWB could only be 10 rnds (for civilian use & ownership). Mags had to have the mfg date on them. High Cap mags (like the formerly standard 15rnd) could be made, and could only be sold to govt agencies, military & police. And they were to be so marked, date, and "LE use only" (or something close to that).
And you were not committing a crime by using a "pre-ban" mag in a "post-ban" gun. The law just said you (as a private citizen) couldn't own, or use a post-ban Hi-cap magazine in any gun.
With the sunset of the AWB in 04, any legal difference between pre- and post-ban at the Federal level went away.
However, a few states passed their own versions of the AWB, some slightly different, some virtual carbon copies without the sunset provision. They are still the law, in those states. NY, NJ, MA, & CA all have some kind of AWB laws that I know of. Some other states may have mag restrictions, of some kind, I don't know about them.
All else being equal (and it almost never is) bigger bullets tend to work better.