Hello.. hoping someone could steer me in the right direction here.

i bought a used single shot 112 223rem. Had receiver coated, redid stock, trigger etc. got the gun all assembled and when I went to boresight, it was wayyyyyy off. Maxing our windage wouldn’t get it lined up. So I tried zee rings, still wouldn’t line up. Next I put a adjustable windage base on, and it finally lined up, but at that point I did not like that setup.
i kept looking and studying. Thinking the barrel must be bent. So for shit and giggles, I swapped barrels with an old 270 barrel I had, just to see what happens.
Same thing, wayyyyyy off. So now I’m thinking either the receiver is not threaded square, or the base mount holes are out of align. I can’t tell
So.. reckon what I should do, or who I could I could send it to, that wouldn’t keep it a year, lol ?
Or, would it be better to give up on it ?