My take on how many rounds down range before getting "serious" about groups is 500 with factory barrels. Then do a total clean and start again. I don't expect really good groups until about 1,000, which is the number recommended by the test centers before sending.
My RPR didn't start shooting until after the first 500 were fired. When I bought my first B14R, 18" steel, I put 500 through it before any serious groups, cleaned and then continued shooting. My second B14R SS HB came last week. Same formula, 500 rounds, total clean, then some more. This barrel started to group very well at about 600 rounds. Put a total of 800 rounds through that day and total clean again at home.
All the above mentioned rifles have shot .166" 5 shot groups (or better) at 50 yards with the same ammo. RPR was sold to a buddy for his kids to start shooting. My original B14R has done much better at times, it has over 15,000 through it now. My new B14R 20" SS HB only has just over 1,100 down the barrel, but has already shown it will be at least as good as the first. Shooting inexpensive TAC 22 consistently around .250" at 50 yds, and has already produced .163" when the flags were consistent. 100 yds groups already under 3/4" under decent conditions. Can hardly wait for some better conditions to really wring it out with quality ammo. Initial shooting done under switchy right/left winds at 36-50*F, both days.
Bore in the B14R 20" was bore scoped before shooting. It showed typical small striations in the groves and on the lands as well as reamer marks on the leade from rifling and chambering. Again scoped after the first 800 rounds and cleaning and most all the groove and land striations were now polished down or out, and the leade tooling marks reduced to faint remnants.
Now if the barrel is a high quality custom, most will shoot very well from the get go after seasoning with a few rounds, especially if hand lapped after rifling. Still, the test centers recommend 1,000 through for best results before testing.
This is my procedure, with my results, your results may vary. I have suggested this to a few friends that have noticed very similar results following the procedure I use. All showed noticeable improvement in smaller group sizes after a minimum of 500 rounds.