The Sierra reloading manual had a short quip about the 7rm being used by a .gov agency, i'm sure a little google-fu could find out if it's still in use.
Some random musings regarding the potential thought process behind the military decision to adopt the .300 rather than the 7rm (not in any particular order).
1). Bore life-
While not a huge difference, it does exist. (according to my barrel life calculator an increase of ~10-20%) running H-1000 in both. When maintain hundreds if not thousands of rifles, the cost savings is not difficult to see.
2). Projectile cost-
In order to get the best possible ballistics from the 7rm, the 180 Berger should be used; agreed? Berger 180's run $51/100pcs. The 220 SMK runs $48.50/100pcs. An offset cost of $250 per 10,000 rounds. When your orders run into the hundreds of thousands, if not millions......
2a). Projectile Availability-
I have no problems with Berger so take this statement as an unbiases analysis. I personally feel Berger does not hold the manufacturing capability that Sierra does. Would it even be possible for Berger to meet the production demands of the .gov? If there was any hope, say goodbye to the civilian market for a good while.
3). Accuracy Potential-
I do not have any loading experience with the Berger Hybrids but we are all aware of some of the inherent difficulties with the VLD's. Most with loading experience also understand how forgiving the SMK's are. With that being said, an experienced handloader could come to the conclusion that, with thousands of rifles, even built to the same "spec", the SMK could & should yield a more consistent accuracy potential across a broader range of rifle than the VLD can/will.
4). Internal Ballistics-
Paper ballistics notwithstanding, the internal ballistic advantage of a bullet weighing 40 grains more traveling at equal velocity (mk248 mod1) can/should offer an increased effect of internal ballistics (impact on target) i.e. Hard target interdiction, penetration of barriers etc.
I'm not trying to sway votes in one direction or another, nor am I trying to wave a fanboy flag in either direction (300wm all the way
). Just my musing of the potential "whys" of the decision to run the 300 over the 7rm.