Hi. I have an M223XR scope mount on my AR platform match rifle that I specifically built for NRA Long Range rifle matches. This rifle was built to accommodate my injuries but yet placing me back in competition. I have mixed feelings about the M223XR scope mount.
I placed an 8-32x BSA Platinum scope with Mil Dot reticle in it. I realize from the beginning that this is a low end scope, but after a full season of match shooting (the latter half being F class matches), the scope is still providing outstanding service in this mount. So yes, you can mount other than Nikon scopes in this mount. The MAJOR problem I experienced was the milling and quality control in the manufacture of this mount. The first mount I used was not milled properly, and I ran out of left windage adjustments in order to zero the rifle. It seems that the base was not milled square to the attachment clamps and didn't mount square. I called customer service and they said they said they would look into it. About a week later, I received a replacement base in the mail without correspondence or explanation. I replaced the mount, and the newer base fit properly and is doing the job.
Pluses for this base. It does provide adequate extra elevation so that this BSA scope can be used for 1000 yard matches. Customer service stood behind the mount, despite the fact that their standing behind the base was a little clandestine.
The down side is that you may have to go through several bases to find one that works properly and doesn't require you to run out of windage in order to zero your rifle.
Leopold makes a comparable base (same style) but almost at 3X the price. I am not certain, if I were to do this again, if I would purchase the Nikon base or go with the more expensive Leopold base.
Just make certain that you are trying to mount a 1" tube scope in this mount, and not a 30mm tube.
Good luck!