I think the SKS got in under the ban because it was a 10 rounder. I think the ban included the following:
Bayonet lug, 30 round mags, pistol grip, flash suppressor. You saw some AK's come in with plain barrels (no flash suppressor or bayonet) and with thumb hole stocks. They also came with 10 and 5 round mags, even though they could handle the 30's. Same with AR-15's. Basically it outlawed the manufacture and sale of magazines over 10 rounds for rifles and pistols. Bayonets, flash suppressors and pistol grips really killed a lot of people. I think you could have one of the banned items on a weapon, but no more. The manufacturers went into overtime making high capacity magazines and flooding the market before the ban and after it was lifted. They are probably flooding the market with them now because of the potential cut off. I did a term paper back in the 80's when I was in college about gun control. I found out that only 3% of all gun crime was with rifles, and only 1/2 of 1% was with the so-called assault rifles. Pistols were 58%, shotguns were 39%. Too much stupid influence from Hollywood. Oh, and folding stocks were outlawed.