You're method is very similar to mine, however I fire groups of a certain charge, not one at a time... What happens if you're best load happens to be 43.3 gr., and after the 43.0 shot; you accidentally pull it a little? You'd think it didn't work well - firing at least
2 shots, so you'll know the rounds really are impacting there... You mentioned a valuable step in your method that I forgot to mention in mine - marking your points of impact in your data book - invaluable reference material.
Also, don't forget to chrono those loads! Loading in the dark ain't fun
Just because your aren't seeing
pressure signs, you might just have a very well-built rifle that has a tight bolt and lockup, and isn't allowing as much head-expansion or leaking primers as usual... A chrono is the best way to see when you're approaching the maximum threshold.. I loaded for a few years without a chrono, and after I used one once - I'll never develop another load without it!