The unsafe side is the broad range that his powder measure drops
I was under the impression, from what other people have said that .4 gr isn't that big of a deal for rifle loads. For my 9mm I load 4 gr. of Power Pistol for 147 gr bullets and 5.1 gr. for 124 gr bullets. At most I get a .05 gr. spread, which works out to the same percentage as his .4 gr for a 26 gr charge. I also have a Hornady powder measure and with PP I found it very accurate and consistent. If the rifle rotor is supposed to be just as accurate, then .4 is a bit much.