That's odd I know that IMR 4831 is smaller in kernel(per grain) than H4831 I have never compared IMR4350 and H4350. I actually have became a fan of the slower Hogden powder but it hangs up the charge bar more than IMR. But that's a simple cure dump the case and go again. I have great accuracy using H4831 and 165's bullets in my 300 win mag loading a few tenths below max. The bullet is sitting almost on top the powder when shaken you can barely hear anything move inside.