Simplest solution would be to view the rifle before you buy it.
And ask about warranty, in an email.
I've seen a few comments regarding warranty and crooked sights/indexing and a few other "typical" norinco m14 "flaws"
When I say Typical, that means just that and has been the case with these rifles all along, for years.
I hardly see it as a warranty issue on a 400 n change rifle.
Just my opinion, not trying flame anyone.
These typical flaws are essentially what keeps the content here flowing LOL and it's been that way for many years now.
When I verify barrel index, there's one "quick test" I perform. Remove action from stock, remove oprod spring/guide and oprod, remove bolt, remove gas plug and piston. Tighten gas lock as far as it will turn by hand.
Lay the rifle upside down on a table so the bottom side is basically level. Insert a 1/16 drill bit , shank end, into hole on bottom of gas cylinder and into barrel. Allow it to sit in place while you look from the rear with your eye low to the bottom of receiver.
Use the receiver lugs and the cutout where the spring guide goes as reference and see if the drill bit is vertically parallel to the receiver legs and oprod spring guide cutout/recess.
Move drill bit side to side in hole to see if it will lean more one way than another. This will give a damn close estimate on whether index is off.
Typically, levelling bars on flash hider an behind rear sight are a good indicator... But as the flash hiders are often out of spec.... The levelling bars only read true if muzzle device is replaced with USGI or an aftermarket device adhering to usgi standards.
My 2 cents.
