My Mark 4 M1 16x40 is built like a tank. It is on it's second set of M1s and has never been anything but utterly reliable/repeatable. When I bought it back in the early 1990s, it was one of 2 Leupolds that I considered to be actual mil-spec. It has enough come-ups to shoot into the next zip code.
To say a few things in it's favor, I have won 600 yd egg shoots with it, and shot a couple of 1.25" 500 yd groups with it (Both witnessed by 24 HCF members). It has been beat on fairly hard for a civilian's scope. There is undoubtedly some better glass out there now, but I'd say I got my $900 out of it. I think they run like $1600 or so now.
Some of the M4 Leupys were in fact "rebadged" hunting scopes. As for those scopes, no different than the 2 Mark 4 PRs I own, or the 3 VX3s I have added M1s to. If they didn't track worth a hoot, I'd not own them. However, if my life depended on it, I would not consider them the equal of a true mil-spec Mark 4 or Mark 8, NF, S&B mil-spec, etc. They may track as well initially, but they are simply not built as tough and I would question their durability as to just how long they could/would remain repeatable if subjected to the harshest of conditions. For general hunting purposes, target shooting, etc., they are more than good, IMO........
