the parts in question are the 551 replica and the upper receiver on my M4, the issue is that when i placed the 551 onto the flat top it was slanted to the left (the angle of the camera makes it look like the whole receiver is slanted but it's straight) the thing is i want to make sure what is causing this problem hopefully its the upper receiver. now in the first photo it makes it look like the front sight is crooked but it is straight i triple checked to see it was properly aligned.
i just received a 551 replica last night and i noticed something on the underside of the sight, it looks like a piece was grinned off or something which may be a factor to why its slanted.
the other probability is the upper receiver itself, the picatinny rail on top is crooked where it seems to slope down to the left. (this is the one i believe is the issue)
any comments that can help, will be appreciated.