Quoted:
Get a refund and get an ARMS #40, and then you won't have to worry again.
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Pass on the ARMS #40, it is garbage. For starters, they cut away the top of the long-range apeture, so that it apperas to the eye to be a buckhorn rear sight. Imprecise. They claim to have done this as an anti-canting feature. BS. It appears they did it so the apeture does not contact the eyepiece of a low rear-mounted optic.
You want quality control? On mine, if you change apetures, the windage drum moves. That's right, you get new windage automatically everytime you rotate the apeture.
To boot, they still finish the sight in that light grey 1970s Colt finish. Matches nothing modern. And the release mechanism is balky, and the fold-down awkward.
The MAD is far better. Sits lower, is sleeker, more practical, finished in black. On a BUIS, I fail to see the need for 600 meter adjustments or dual range settings. The MAD offers 2 apeture sizes to fit the combat conditions, and a 250M or 300M zero will take care of anything you would be shooting at with iron sights. Lifts up and down easliy, with gloves, and has a detent in each position.
Mine is not crooked. Check your mounting position.