This is only part of the equation though. If it’s all over the place on subsequent trips, is there an issue with rings? Does the shooter not know how to read wind? Etc…
At a minimum you’d need to swap in a different scope, repeat the same tests, and if that one was spot on then put the old scope back on, and do the test again. If it wouldn’t hold zero again, then yeah looking like that scope has a problem. And that’s a sample size of one so it wouldn’t mean that brand of scope doesn’t hold zero and is junk across the board. It just means you have a bad scope.
You're correct. I was in a hurry, but should have posted a more complete response.
I was actually thinking about it later and realized he hadn't shot the rifle with a known-good scope, so we really have no idea if the bad groups are the rifle or something else.
As a side note, when I stopped using Leupold scopes, my groups became more consistent, and load development became really, really simple.
It does not matter to me if other people trust and use Leupold scopes on their rifles. I used them and liked them for years until I started actually checking zero and noting that it kept moving. I still like the company and the employees I've met. I still have many friends who shoot the Mark 5 on all their competition guns, and some of those guys are the absolute best at our sport. I have also seen many of them have problems, and they all check their zeros before every competition.
Last year, I zeroed my 6.5 CM built on a Tikka action with UM rings and an NX8 scope. I then tossed it in a drawer in my truck in a very thin rifle sleeve, along with another rifle, a couple of tripods, and other gear. I then drove from Washington and back for three matches in California, North Dakota, and Wyoming. I made the podium at all three but didn't adjust the scope once through all of that.
If I could trust Leopold scopes, I would use them because I get 50% off, but I can't, so I buy other scopes at retail with no discount whatsoever.