Of course the factory loads by volume, but in order to achieve the desired volume the powder would have had to have been weighed at one time, or they would not know what the volume would be. Once the reloader sets his powder measure he too is loading by volume because the powder charges do not weight the same, and I've chronographed enough rounds to believe the same is true for factory loads.

Now as for my so-called Match Duplication load, that is speculation on my part because the only thing a reloader can duplicate is the velocity because everything else is a variable, even within the different lots of the same components. Now add the differences in firearms even in firearms of the same model, caliber, and barrel length, and what is this in one, is something different in another.

The load I mentioned using 42 grains of IMR 4895 was derived from data on US Military Ammunition in Cartridges of The World; 9th Edition; Chapter 17, U.S. Military Ammunition; Cartridge, 7.62, Match, M852...
Then they list all the specs with propellent listed IMR 4894, weight 42 grs.

Now I looked at some of my saved chronograph data and I did not Chrony this load, and if I did I do not have any record of it as I had the basic Chrony and had to write the fps down and then do the match at home. But I will say this, and I was wrong I shot the load at 200 yards not 100, and while I have no measurement of the groups I was impressed. One group was nice and tight, the other a more laid back group was still all in the black but a bit opened up.

I cross referenced this load with my loading manuals and it was certainly within all safety margins for the powder charge and bullet weight and type.