I've done a little "market research" as it were lately, on MR internal frame rucks. I recently traded out for one so I could test it out for myself. The particular bag I have is the "Grisly" which I assume is pretty close to the 6500. I loaded it up, to about 45lbs, and took it out for several spins. 4, 6, and 8 miles. Rolling terrain, temps in the mid-40's. I was pretty much disappointed. I though it would ride a lot better than it did. It gets the job done, I suppose, but I thought with MR's reputation, it would be a lot better.
I just don't like the internal frame and suspension anymore. After testing out all the pack bags on a Crossfire external frame and suspension, I guess you get used to a certain ride, and when you go back to other systems, they just don't compare. Although I may be a little biased on the subject, but I would guess most guys that try them both out would agree.
First off, is the internal frame. Such as it is. You get these two sets of stays, one in the bag itself, and another in the Futura style harness. I just don't think this is beefy enough. It barely works for 45 lbs and I wouldn't want anything over that. The load can twist and move around, if you get off-level, or go into a recon shuffle.
The suspension relies on a heavily over-padded, super stiff waist belt. The shoulder straps are basically there to hold the ruck against your back. And there's is some validity in that approach, however, the waist belt is so stiff your hips can't really articulate in uneven terrain, much less move at a run. You are basically locked into a walking pace. Which if that's all you need to do, GTG, but for .mil applications you might need more.
The suspension padding hugs you from neck to hips, which sounds good on the face of it, but soaks you through with sweat, even at lower temps. So at first blush. you're thinking, right on, but temperature regulation could be a challenge.
And yeah full disclosure I work for Crossfire now, so if I just wanted to motherfuck the competition, I could say all this just as marketing strategy to pimp my wares. But it's not that; before I went to work for Crossfire, I wanted to try MR rucks out for a long time. I figured if the big dogs are using them, they must be pretty good. But the price point kept me away. When I finally did get my hands on them, I just gotta say, I am not that impressed.
But hey, any of you guys with more experience with them, chime in here. Did the issue rucks get the job done for ya, or what?