Shanghai B2-3 sight problem

Hello,
so, today I received my Shanghai B2-3 air rifle. After examining it, I noticed that the rear sight is tilted to the right. When I placed optics onto the rifle, the optic was tilted to the right too, which means that the cuts where the scope mounts go are tilted to the right, too. Is it there a way to dissasemble the rifle so I can rotate the barrel to the left to center it, or do I have to get a new rifle? Thanks in advance!
 
Not being an expert in this topic, my common sense tells me that the answer is "heck no". The grooves you mention are (I assume) the dovetail grooves machined into the top of the breach assembly, not the actual barrel of the gun. That assembly also has the various ports, pin holes, and screw seats machined into it as well, doesn't it? If that is the case then simply "rotating the barrel", which is actually means rotating the machined assembly, will do nothing to correct the misalignment of the dovetail grooves and the other machined features of the breach assembly. As I said, I'm not an expert but all of my exposure to air guns thus far argues against you finding success in manually correcting this defect.