@ Cluster Bomb
I pretty much agree with most of
onebadcaballero's recommendations, however I'm unfamiliar with the KNS sight post and I never really had a problem with the stock front sight, so I've left mine alone. Also depending on how you use your rifle, you might not need the Murrey's kit. I don't use soft primered American made ammunition and my handloads use either CCI #34 mil spec primers or Russian made KV24N, 7.62x39 Berdan primers. I also make sure that the firing pin and channel are kept completely free of oil, grease and dirt. When you hold the bolt in your hand and turn it end over end, you should be able to see and hear the firing pin moving freely in the channel. With practice, you can do this even with the rifle assembled, just make sure it's unloaded and the hammer is cocked.
For your initial cleaning to remove the cosmoline you'll probably need to disassemble the bolt as stubbicatt suggested, but unless mine get dropped in the mud or otherwise totally trashed, spraying the pin and channel with B12 Chemtool followed by blowing out with compressed air seems to work fine.
If you should happen to change your mind and use the high capacity detachable mags, you really need to read up on 922r, it's not near as simple as adding 3 or 4 American made parts and while the ATF isn't busting down doors looking for 922r violations, if you ever show up on their radar in a negative way, being in possession of an illegal rifle WILL be used against you in one way or another.
This is a pretty good site to go to for basic 922r info.
http://www.tapco.com/section922r/
I quit using the detachable magazines pretty soon after I got 'em, they're a god-awful shape if you're trying to carry extras and the rifle is plenty heavy enough with the stock magazine and 10 rounds. Get ahold of a few of the 10 round stripper clips, they're light and a convenient way to carry extra rounds. They also load like greased lightning into the stock magazine and unlike M-16 strippers, they'll last forever if you're even halfway careful with them. Unfortunately, I never found a detachable magazine that they worked worth a darn in.
I'm not very well versed in the latest and greatest as far as scope mounts go, but I've been very happy with the Choate drill and tap mount I got several years back. It's kind of heavy, but its the only mount that I'm personally aware of that I would even THINK about trying to mount a heavy nv scope on.
The biggest disadvantage of this mount to me aside from having to modify the rifle, is that it prevents the use of stripper clips. There are "Scout" type mounts available that you can use with a medium or long eye relief scope. These mounts leave the top of the receiver clear, but I don't think they'd work at all with a nv scope.
If properly mounted, the Choate mount allows you to remove the top cover and bolt fairly easily, I mounted mine a little lower than the instructions recommended so getting the bolt in and out is kind of a pain, but still doable. I figure it's a decent trade off since it put the scope about as low as it could be while still retaining the ability to use the iron and night sights.
Whatever you do, steer clear of the scope mounts that replace the receiver cover, a buddy of mine purchased one and it worked every bit as well as you'd expect of an easily removable part that gets battered by the fast moving bolt every time you shoot the rifle. NOT a good thing to mount a precision optical instrument on!
I'd also suggest that you not equip your rifle with a recoil buffer, if they were needed or desirable, Mr. Simonov or the Yugoslavian engineers that redesigned the rifle would have put one in it.
Fun fact: The grenade launcher on the 59-66 is actually designed to work with NATO spec 22 mm grenades!
No wonder Uncle Joe never really trusted Tito...
