Re: BDC for a Redfield.
I might have something for you. Somewhere in all of my clutter I have a pair of very old after market knobs and I don't know what they fit but it might be that they fit Redfield being as that was what I was using long ago.
Take the cover off the elevation adjustment and take a pair of calipers and measure the inside diameter of the cover where the threads are and post it up. I will then do that to the knobs and we will see if they are close enough that they might work.
The Smokin Fur Rifle Club