I have a Yugo 59/66.  I was thinking about taking the grenade launcher and grenade sight off and putting on a muzzlebrake.  I'm not really worried about retaining any collector value but I actually thought making it like a plain 59 would retain the value.
Opinions:  should I bubba it or leave it alone.

Since you do not care for collector value and if you think you can do it, I would go for it. Might as well have something on that is actually useful.

Wouldn't 922r then apply?

It would apply only if the parts that were replaced were not damaged or were functioning properly.  The way that "I read" 922(r) is that a part that is no longer functioning or otherwise damaged may be replaced without requiring the 10 or less foriegn parts necessity.



Seems that you might get into a sticky situation where the gas block and front sight/bayo block would have to also be removed and refitted (because they are damaged, of course).  And you still will have to deal with a muzzle end that has exposed threads if you are converting to M59 features.

I don't own a yugo but i'm guessing the current yugos in the U.S. are U.S. complaint, as long as it stays as it is? I thought the yugo, or the sks for that matter, was complaint based on having U.S. parts put in by the importer. If so, swapping out the g. launcher for a U.S. made brake or flash hider would just add another U.S. part.  

Since there are NO US made parts put in SKSs by the importer, your supposition is wrong.
The Yugo 59/66 and other SKSs with a bayonet are imported as curios or relics, which is how they qualify for importation.
Modifying an SKS that was imported as a curio or relic takes it out of that status. If the modified rifle could be imported 18 USC 922(r) does not apply since it only prohibits assembly of a rifle that cannot be imported. If the modified rifle could not be imported, you must comply with 18 USC 922(r).
There is no "damaged parts" exception. The regulation exempts replacing parts on a rifle imported before the effective date of the regulation - 11/30/90.
Unfortunately, AFAIK, no one has applied to import SKS rifles other than as C&R, so there's no way to be sure if the gov't would have approved the application to import.
The best guide would be to configure the rifle like the post '89 Chinese rifles - standard ten shot non-detachable magazine, no bayonet and no muzzle device. In that configuration, the rifle met the redefined "sporting use" requirement and was approved for importation.

What Poly said.

Doing what you mention would take it out of its original configuration, thus removing it from C&R status.  Then 922r would apply.   You'd have to remove enough foreign parts to bring it into compliance - but removing the brake and grenade site would count.

As I understand it, 922r is a subtractive law.  You have to REMOVE x number of non-US parts.

Now that I re-visit my post about changing out the front launcher on an M59/66 for the standard M59 bayo lug and sight, I would have to agree with Polythenpam's assessment.  Such a change would void C&R.  I was wrong (and not "misspoken" like so many politicians these days!), just plain in error here.  My apologies.



My interpretation of replacing damaged or lost parts comes from the line "original military configuration" found in the explanation of C&R status under Title 18 USC § 925(d)(3).  So if your Yugo stock cracks and you put a Tapco T-6 on it, then the gun would fall under 922(r) and you would have to begin playing the ten or less foreign parts game.  But if you replaced it with a stock of "original military configuration", or more specifically another wooden Yugo stock, then it would still be considered C&R.  Otherwise the vast majority of Yugos which are mis-matched from the start would not be Curio eligible.



And if all that is perfectly clear, you are doing well.  So, please disregard my words about removing the launcher... unless you want to replace it with another identical launcher, or go fully 922(r) compliant.

I guess the decision has been made.  No changes.  What if the gl were drilled out like a muzzlebreak.