Thanks to all - I read it.
I clean my .22 RF after each use, the nice bore just sparkles, no baked on debris ring in front of chamber, and produces 1/2 inch groups at 50 yards at normal temperatures, above 50*. I try to limit max ranges using hi velocity ammo to 75 yard. The combination of my Douglas barreled M77/22 and the Winchester Power Point 40 gr. hollow point is good for head shots on tiny rodents like gophers in thick alfalfa.
Now for the disparity;
This bad accuracy event occurred just after I pulled the rifle and ammo out of my warm vehicle and put a bunch of bullets into the same hole - Winchester Power Point 40 gr. hollow points (favored rodent ammo). Then I put the rifle and ammo away but in the cold and shot my .22-.250. After the .22-.250 session I resumed shooting the .22LR and then my accuracy was not accurate - like flyers, some 1-2 inches out. My Winchester Power Point 40 gr. hollow points were icy cold to the touch. Upon reading the label in the nice silver colored box I saw - " Lead Hollow Point, Lubaloy* coated" (* apparently copyright Winchester) The nice little copper plated bullets do not appear to be greasy and have 4 annular grooves pressed into the bullet just below the ogive. Examination of each bullet with a 10X Hasting triplet magnifier showed the bullets to be covered with a shiny translucent film with concentrations, of which, in the annular grooves. Apparently this is the Lubaloy coating. The surfaces of the copper plated bullets are covered with a patina of tiny dings & dents, like they were tumbled. The translucent coating is hard & lacquer like.
My guess is that the Lubaloy stuff congealed in my icy cold barrel and combined with normal powder fouling screwed things up. Possibly the Lubaloy stuff was applied in some tumbling process associated with the copper plating that caused all the tiny dings & dents.
In comparison my CCI standard velocity .22LR have a much smoother surface but appear to be greasier.
I have not resumed testing, like no .22LR cold day shooting, since the last event thus no additional shooting data for an update but have been unable check out & compare .22LR ammo for the next cold day shooting. .22LR ammo is in short supply but the high price stuff including biathlon type ammo might be available.