Re: How close is close enough?
Whether it'll affect your results depends on things unknown to me(but still existing).
Once you've actually tested for best seating with a couple guns you'll come to recognize that 5thou CAN have a big affect,, but then it might not.
My seating does not vary by even 1thou. It is for the most part -exact.
My shoulder bumps are also pretty damn close to exactly 1thou, to begin(settle variance can shift ~-.0005 over time).
So I know that it can be done & how to do it.
I also know what mungs it all up:
-Not qualifying ogive radius
-Not using inline die seating(with an arbor press)
-Not turning necks to same thickness
-Not trimming necks to same length
-Seating bullet bearing too near neck shoulder junction
-Big variances in bullet bearing
-FL sizing necks
-Inconsistent/bad mouth preps
-Bullet mismatching seater plug, bad contact angles, bottoming, or contacting too high on nose
-Inconsistent neck lube
You're probably thinking this is ridiculous, but with only a few more items added you can also address runout, headspace, capacity variance, and ES.
This allows for better quality in load development.
Anyway, test for best seating with your load, work down this list, & decide how and where you should go with it.