Thanks guys, this forum is great.
Slenk, I was shooting using shooting sticks on the forearm. I'll definitely try again with the rest behind the hinge. It's also easy enough to add the O-ring like you suggest. I'm not going to turn down any possible fixes that are that cheap. If single shots are fussy about rests, I can also try a few groups offhand to see if that helps things.
Bearpaw, thanks for the suggestion to do a more thorough defouling. I'll admit that I still had blue on the patches after my first attempt. I'll get it clean before going back out to the range.
If none of those things get the rifle Minute of Deer, I'll probably call it quits. Working on the crown, hinge, or other real gunsmithing just doesn't seem worth it for this quality of rifle. I'd be too embarrassed to sell it to anyone, but maybe I'll contact the store I bought it from. If I'd be too embarrassed to sell it, maybe they'll feel the same way.