Got to see a Mk 4 HD in person while in Alaska last week while the Rep was visiting Granite View Sports. Great shop by the way. Quite a nice scope, turret feel, reticle was nice. Was a 6-24 model with christmas tree. I asked the rep if she was familiar with the Rokslide Drop Tests. She said "We are and our military tests are far worse than that" or something to that effect. She seemed quite knowledgeable and I was pleased to see the drop tests are at least on their radar. After a lot of discussion, I got the impression this scope might be able to pass. Fingers crossed because if it will pass I will buy one and drop my own. If it fails miserably, I won't bother.