Mounted an older 3-9X40 Leupold on Ruger #1 .243 using supplied Ruger base.
Immediately ran out of horizontal adjustment during initial sight-in. (Still 2" left @ 25 yards).

I've encountered this several times when using the older Leup's, but it has always been an elevation problem.. which I solved with shims..

Need recommendation for a set of rings that offer some decent windage
. BTW, was using Leupold rings.

I really like the S&K horizontal rings as well as Talley detachables.

Any input would be greatly appreciated!

I am not sure what you mean by the Ruger supplied base unless you mean the quarter rib.

The Burris Rings with spherical inserts will provide a lot of adjustment.

Sounds like you have a quarter rib or barrel that is crooked. Or you got one of your rings from the first mounting episode reversed.