At 9/16", you would seem to have the lower of the two most common possibilities, which would actually work against my theory, so, I'm back to square one. Regardless of placement on the target, what size group do you get?

Which model of rear sight is on your rifle? There are photos available from the home page.

Cannot comment on the load, or your pistol analogy, as I don't shoot very much anymore.

Some pointed bullets (usually the longer 180s) will feed OK, others won't - the receiver parts were very precisely profiled for the long 220 gr. RN, and they really didn't care about anything else.