From my limited experience I'd tend to agree that "breaking in" a barrel has its greatest effect on ease of future cleaning.

When I got my Ruger M77VT MkII 22-250 I hand lapped the bore with JB Bore Paste right out of the box. Then I did a 5 shots then clean routine for the first 40 rounds. What I noticed was that after each 5 shot string the cleaning became a little faster and easier. There was also less evidence of copper buildup after about 20 shots (the patches stopped turning blue/green when I ran copper solvent down the barrel). After that 40 shots or so I no longer have any significant copper fouling and I can clean the barrel spotless withing 10 patches. I also have found that I seldom need to use a brush anymore. I scrub with a bore brush about every 100 shots. For the most part it just takes a few patches of solvent followed by a few dry patches right after I fire my last shot of the day while the barrel is still warm.

As far as accuracy goes I cannot say. I lapped the bore before I shot the rifle so I have no before & after experience with that, and the group sizes have been fairly consistant since the beginning. The only improvement has been reduced fouling and easy cleaning.

Mike