You need to be very, very careful if you plan on tinkering around with an SKS, especially if it's one of the recent Yugo 59/66 models.
Enthusiasts argue about this topic year on year, but here's a rough summary and I'll use the Yugo as the specific vehicle.
The 59/66 was imported into the US as a Curio & Relic - that status removes if from the provisions of importation regulation 922(r). If you then make
ANY change to the weapon, it immediately loses its C&R "protection" and once again becomes liable to 922(r).
Prohibited features will then include:
01. Grenade launcher
02. Grenade launcher sight
03. Night sights
04. Bayonet
05. Bayonet lug
And a 59/66 has every single one of these, additionally 922(r) requires you to play the "10 or less" game, whereby your rifle cannot have more than
10 imported parts.
Therefore in order to bring your SKS into 922(r) compliance you have two choices. Either remove all prohibited features as listed above or bring your
weapon into compliance by having no more than 10 items from the imported parts list.
The literal interpretation of the various laws did at one time make it illegal to remove a bayonet from a Yugo SKS, and illegal to fit one to a
Chinese SKS - it may still, they are very complex.
Get it wrong, and it's 10 years in jail.
So you'll perhaps understand why I recommed that you contact J&G Sales in Prescott and have them ship you a cheap WASR AK-47 for $400 and save
yourself from the following :
a) About $300 (rebuilds never work out cheaper)
b) An SKS that doesn't feed reliably from a 30 round magazine
c) A lot of personal time
d) A felony conviction
Your call, but don't say you weren't warned