I was helping the neighbor sight in his deer rifle today. Not a high $$ rifle, but suitable. It’s a Savage Axis, 308, kinda a cheap scope.

He’s also in a wheelchair, has an adjustable bar to help line up the gun. He’s used this gun for 4 years or so, usually a few shots to confirm the zero is all it takes.

He hunts some great spots, edge of small town, deer half tame. He usually bags 2-4 deer a season.

We start shooting, going well, plenty fine for the 50-100 yard expected distance. As we go to a different brand of ammo, things go downhill. It starts where now we are ‘off paper’, even with minor scope adjustments. I end up walking to 25 yards to get back on paper.

Then back with him, the shots don’t stay true. I started closer evaluation. I found while the rings themselves were tight, the base of the rings were loose then slipped out of the rear base, not good.

I found most everything was loose, everything. I went & got my supplies then remounted the scope. After that he was quickly sighted in.

I was bummed I didn’t catch it earlier, after ammo expended. I had similar happen 25 years ago. I bought a rifle & let the shop mount a scope I bought at the same time. A few days later I went to the range & couldn’t zero the gun. I noticed the loose scope, then left due to no tools.

Just a reminder for those getting ready to sight-in.

A few years ago I upgraded the scope on my 308. Quality components here -- GA Precision gun, Defiance action, Nightforce rings & optics. I zeroed the new scope at 100 yards without issues -- maybe 5-7 shots, and it was drilling them in the center.

Then I set up a target at 500 yards. Elevation was pretty much dead on, but wind was pushing me around horizontally. IIRC 4 or 5 shots on a waterline that was a touch less than 2" vertical variation. Then W...T...F...flyers high and low. As in 5-10 inches up or down. I felt a wobble in the scope as I was checking for good parallax.

Hmmm...scope is tight in the rings, rings are tight in the rail. Ruh-roh, the rail isn't tight in the receiver. Turns out both screws holding the rear part of the rail to the receiver had sheared off. My local 'smith had a heck of a time extracting one of the screws from the receiver. He suspected that the rail's screws were over-tightened from the get go, and the new heavier scope might have just been enough to break them.

Sometimes odd things occur with optics mounts.

Good that you had the tools to fix it with you. I've had enough range sessions cut short that I now have a huge range bag with pretty much everything I could possibly need in there to fix sights, punch out squibs, change batteries, mount optics, etc. It's like the gun-guy version of my wife's "mom purse". It's solved a lot of problems over the years...more for others than for me. It's not set up to drill and tap sheared screws, though .

When you first said you were off the paper with different ammo my eyebrows raised and thought it has to be scope settings changing.
Glad you got it fixed.