Ok here goes, I'm curious about magna porting on a 7.5" Bisley with a scope. How well does this work? I'm worried about fouling that close to the optics. Will I NEED to have a clear cap or will the blast be far enough away to not affect it?
I'll be using a frame mounted base with a 2x leupy.

How close is the objective to the porting? Take a white piece of paper and wrap it around the objective, secure it with tape or a rubber band an fire a cylinder. If the paper remains white you shouldn't have any worries.

Save your bullets, its not a problem.

In response to your asking how well the Mag-na-porting works for your Bisley, I would say, not well enough to justify the price. I had a .270 Winchester Encore barrel mag-na-ported, and it helped immensely. However, the much lower pressure .44 mag (I am assuming your Bisley is a .44) will not benefit nearly as much. You may notice some decrease to muzzle rise, but at the cost of increased noise and blast. I would recommend saving the money and purchasing additional ammo to practice with.