Newbie: Advice on scope alignment

I'm shooting JSB 18.13 ,Air Arms s510 , 2900 PSI , bench rest with UTG 4x16 44 25 yards. The elevation works perfectly the windage is "cranked " ALL THE WAY to the right and I still have to put the mil dot one to the left. When I do that I'm spot on approx. 1 inch groups . I called UTG to find out what I'm doing wrong and he told me to fill out a replacement form. I'm sure it's not the scope , it's something I'm doing wrong. TIA
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Sometimes barrels do not align properly with the receiver due to manufacturing tolerances. I have seen this condition in airguns from $100 to $3500, springers and PCPs. The solution is to use adjustable rings like Burris Signature Zee. Optically center your scope and then sight it in close with the ring adjustments and use the turrets for final minor adjustments. Takes a while, but when compete your scope will be operating in the sweet spot for adjustments and the clearest part of the lens.
 
First of all get a mirror or hold scope bell up to bathroom mirror under very bright light. Have scope adjusted to setting you shoot with. Now look in scope while bell end is completely flat against mirror. You should see the crosshairs reflection. Adjust until it matches crosshairs in scope.

Definitely get FX no limit, Burris Signature Z, BKL, or any other fully adjustable rings. Zero the rifle as close as you can by adjusting the rings, then use your turrets to fine tune.

Before you do any of this, you might want to switch out scope & rings to see if any other combo works. I like to center all my scopes but some spring guns don’t do well with adjustable rings.

This problem is one reason I prefer open sights on any gun as an option. With see through rings if scope doesn’t match the open sights you know right away scope or barrel band has been bumped or scope is defective.