Man, I hate to do this more than anything...but this is ALL Marlin's fault.
I've gone over as many as I can physically find in my area...but the 3/8 rail that is currently cast into the 60 & 795 quite often is not true/plumb...and definitely not .43" wide all the way down it's length. And it seems to be affecting not only new Marlins, but also going back to 2001's!!
I'm getting mostly measurements of .43" to .46" down the length of the rails.
While this is VERY annoying, it's also fixable
....one simply has to break out the files and work the rail a bit until it's down to proper tolerances, then repaint with Krylon Flat Black or Brownell's Bake-On for a longer lasting repair.
So before you wonder WTF? about your scope or mounts...start by looking at the rail with a digital caliper. In fact, it's best to do so BEFORE you order scope mounts/Tech-Sights.
I will point out that strangely, my 2005 Marlin model 60 is just fine. So it's not every one, but a good percentage....which usually means someone in Action Molds at Marlin ain't always checking things properly.
But heck, even with a screwy rail, they're so inexpensive & good shooting, a little extra rail work is worth it