l can put 200 or so through before l am cleaning and really am only getting powder fouling with minimal copper out of both mine and my sons 17 ackley
they both have match grade barrels that the throat is polished when cleaned at 200 or so
my sons barrel has probably around 1500 shots through it now and mine has around 2500 shots to its name
they are both reloaded using IMR 4227, rem 7.5 primers 20gr zmax bullets and reformed PPU 22 hornet cases
the elements you had against you would have made for a difficult day shooting, sometimes barrels need a few shots to settle down before shooting their best, sometimes you will shoot better after a few shots when you settle down
and sometimes it takes quite a few shots through a new factory barrel before it will show its best shooting precision, this is what it sounds like what's happening to your rifle to me but you need to pick a brand and stay with it IMHO, if you want to try something else clean the bore then stick with that till you dont want to anymore
the stories about 17's being foulers are from old factory barrels that were not made very well, the newer factory barrels are a much better grade
my last 17 ackley barrel was a douglas that is not a match grade barrel and l shot more than 10,000 shots out of it,
it was still shooting well when l had it rebarreled, the smith asked why l was doing it and my answer was l had a new barrel
sounds like you are getting to like the little 17
here is a pic of a sighter group l did with my sons 17 last week, the first cold clean bore shot out and 4 shots in the group
“If you do not read the newspapers you are uninformed. If you do read the newspapers you are misinformed”. Mark Twain