My son saved his money and bought himself an SKS a couple years ago, thinking it would be a cheap knockaround plinker. Unfortunately, it has 'grenade sights' on it, and they are useless (we generally aren't in the habit of launching grenades other than the occasional verbal one my wife may launch at me about once a month...
just kidding dear, really 
), but as I understand it, you can't make any 'alteration' without it becoming an 'assembled' rifle which then has to have only so many imported parts. Even if taking something OFF isn't an 'alteration' of course the issue is still important in case sometime he wants to repair or replace some part or other on it.
What is the deal with this stuff? I've looked on several SKS-oriented sites, and even Tapco sells an 'SKS compliance kit' but it looks like that kit only has 8 'U.S.' parts out of 20 the regulators list, and an 'asssembled' rifle can have no more than 10 of the foreign parts. I don't really understand the parts math or what the alleged purpose even is. Supposedly it even differs for different vintages and manufacturers of the guns.
Anyone understand this stuff?
(Yeah, and I KNOW - one MORE reason to just chuck the crunchentickers of various sorts and get leverguns...

)