My zero used to wander all over. I'd shoot down at the OTC and fire a nice tight 5 shot group. I'd reload the mag and shoot another nice tight 5 shot group. The only problem was it would be an MOA or more away from the first one. That went on for months. Once I got the position thing down, it never changed. It took a long time to get there, but my zero is now dead solid.

Inconsistent can mounting could certainly be the culprit. Shoot it, remove the can and reattach. Shoot again. That should tell you.

Seriously, you need to get a .22 trainer. They weigh 1/3 as much and the bullet is in the barrel for three times as long. They are magnifying glasses for problems. They're also a lot of fun to shoot. An accurate trainer and 2,000 rounds of match ammo will teach you lots. Plus, you'll get to shoot the .22 side matches in Pueblo.