Priming the KRB is tricky and even more so with a low-mounted scope. I would go to medium rings and then just work on positioning that primer with your fingers. I tried a straight-line capper and my usual result was flipping the primer into a worse position than would have been the case with bare fingers. Some tell me that with practice at positioning the primer, the effort is lessened. Since my barrel is now back at Knight, I've not had enough practice to see an improvement. A capper could be devised that would neatly position the primer, but I've not seen such atool yet.

maybe??

So far as scoping - firmly afix your scope, remove the hammer/trigger assembly and breech plug - sight through the bore at some distant object - center object in bore and then set the crosshairs to intersect a bit below that same object. A cardboard box can be used to steady the rifle while making this adjustment.