This isn't about how accurate a given reloading beam scale is, the question is how accurately can it be read. I have a RCBS 505 that I've owned forever and (it's getting rather beat up) am looking for a new beam scale. One frustration I've always had is reading the pointer. 0.1 grains barely moves the pointer a hair breath from the scale center. So unless I hold my breath, squint with one eye and make sure my eyeball is level with the pointer (to avoid parallax) it's difficult to tell if the pointer is exactly in line with the scale center line. I'm looking at the classic Ohaus M-5 which has a vernier scale but what are the hash marks equal to? 1 grain? 0.1 grain? 10 grains?
I load pistol cartridges predominately and most loads are less than 10 grains. Another peeve of mine, if you have ever dealt with any type of instrumentation you know the most accurate (and easy to read) is an instrument where the maximum values read is equal to the maximum value you want to read. So except for maybe the 458 Lott or 50 BMG the maximum scale for any powder would not exceed a maximum scale of 100 grains not 500 or 1000 grains. For a pistol scale 25 grains would be enough.