I think a lot of it has to do with a clean bore having more friction than after its had a couple rounds run through it & also once you've shot a couple rounds thru a clean bore the fouling allows for a tighter seal to the rifling & all the expanding pressure staying behind the bullet & pushing it allowing for greater accuracy? Seems to make sense but I could be totally wrong??? All I know is my 10/22 will have a couple flyers in each group for the first 10 or 12 shots if I have thoroughly cleaned & scrubbed the bore, which I don't do very often. Usually I just run a patch thru 1 quick time with hoppes or rem bore bright & pull a bore snake thru about 5 or 6 times & it will stay pretty consistent from the first shot on. Most of the diff is me I think. If I'm not going shoot for a while I'll run an oil patch thru it but clean it out before shooting it next time.