First: I don't know what I'm talking about!!n Fortunately, we have Unclenick
who does know what he talks about.
Case volume/load density can sometimes play a part in spiking pressure.
Decades ago, the shooting magazines had frequent discussions about subloads of 4831 wrecking Springfield/Mauser strength rifles on rare occasions.
Odd things can happen when powder has too much space as the primer flame occurs.
I don't pretend to know if there could be such a problem with the OP's load.
Consider a gasoline engine can be wrecked by detonation (pinging) in the combustion chamber caused by lean mixture.
Accurate Powders had a big red loading manual. I there they talked about the challenges of loading safe pressure loads for the 45 Colt (huge case) in semi-strong guns. Now,I AM NOT recommending loading anything here! I recall in the notes ,for a bulky powder that would give some case fill,they suggested Nitro 100. This powder is so fluffy they only fit 12 oz in a 1 lb powder container. I can't tell you how it works.
As far as polishing chambers for a solution.....Did S+W sell you a rough cylinder? If they did,maybe S+W will fix it. If its not noticeably rough, suggest you NOT grab the Dremel or cordless drill and whatever bore mop or dowel or brush annointed with Clover Compound or Flitz or Barkeepers Friend or whatever abrasive is suggested.