My old Daisy pump-up .177 pellet rifle died a couple of years back but had "122" (squirrels) written on the stock over a few years. They've come back with a vengence, so I picked up a Gammo break barrel this time. It came with a cheap scope and a better" looking" set of FO irons that can't co-witness. It also had a sorta-kinda silencer for the noisy springer. Max pellet speed is rated at 1250 FPS with the trick pellets
I went ahead and mounted the 3 power scope and "tried" to zero it at about 15-16 yards. I finally got it to within an inch for three shots from a steady rest. I came back a few hours later and it was off 3". It wasn't me. It was shot with a good rest at a 1" circle (squirrel head size). I tweaked it a skosh and got back to 1" groups again.
If it's off again next timeout, I'll remove the scope (does "look" pretty good through the 3 power, and I have to thread shots through large oak and other trees). I'll try the irons that has a good looking fully adjustable rear and 1mm front FO., and hope it'll start to group some better. PS the scope instructions are to "bore sight?" and then tweak for 50 to 100 YARDS.

My longest squirrel shots with be less than 25 yards if they are chased to the top of some trees.
I shoot into a steel pellet trap I welded up some years back. At first the scope shot 5" high and about the same right, so it missed my trap. The trap is mounted on a square 1/2" plywood backer. I really had to crank the scope adjustments a LOOONG way to bring the hits in closer. The verticle adjust got hard to turn before hits were on target . Adjusting left was fairly easy.
Those first pellets zinged right through that ply and disappeared into an old oak tree trunk. I think I'll get some heavier HP pellets to try for consistency and stopping power.
Any suggestions about shooting break barrels is appreciated. My experiences with pellet guns is limited to pre charged pump ups ( only 2).