Bob,
These LRH's look like they are based, roughly, on Rigby/Lapua brass which is .589\.588 body diameter.
The RUM's have a body diameter of .550 but are rebated so the head is .532.
Since the H2O capacity is about 110 then they are a short version of an Ultra Mag.
If those velocities are coming from 26" barrels, then I'll bet the pressures are much higher than SAAMI maximums. The 7mm LRH is moving a 195 bullet about 200 fps faster than a 7 RUM will move a 175 using Nosler's loads. I doubt if there is any laboratory tested pressure data.
Also, chambering them in M700's exceeds that action's design limits for barrel shank wall thickness. Sooner or later the combination of high pressures and inadequate shank thicknesss will result in failure of some sort. Read Dan Lilja's and Jim Borden's papers on that issue. Both are mechanical engineers so should be listened to.
Pretty good reasons to stick with your Mashburn.
