I have an SR-22 purchased in 2013. It has at most 500 rounds of mostly lead through it and the rifling are almost gone! Has anyone heard of soft barrels from Ruger?
The SR22 is notorious for leading. Scrub the barrel, using lots of Hoppes, and I'll bet your rifling is 100% intact. The rifling is shallow on the SR22's. Unless the bore has been overzealously cleaned, steel always wins over lead. WAYNO.
I don't have one of those Rugers but 500 rounds will not wear out a .22 barrel, nor will 500,000. It doesn't take much rifling depth to spin a .22lr bullet.
Mine did the same thing once with a older box of thunderbolts. Took a little TLC to clean up. Has not done it since.
I think it was famous gunsmith PO Ackley that ran 100.000's of thousands of rounds thru his only .22 rifle, I can recall the make or model. But he only cleaned the action! Never ran a patch or a brush thru it! I need to look thru my Ackley books and find the story! But in this case, I have ran across some very soft lead, that will lead up your bbl in no time! My customer was using .22 that was an import I had not heard of before...It was so soft you could pick the bollit apart with your fingernail with ease...
I have worn out myself and several bronze brushes trying to get the lead out of a barrel. I found an easier way. Bronze wool, like steel wool but made of bronze. Rap it around a worn out bronze brush. Removes lead easy. Will not harm your barrel. I have also used the Lewis lead remover. Works great. I don't think it comes in 22 size. http://www.brownells.com/gun-cleani...ead-remover/lewis-lead-remover-prod21587.aspx
Your pictures don't really look like there's leading but they are small and not perfect pictures. Perhaps you are hoping/thinking that there is leading and by "cleaning", the rifling will be deeper. Is the gun accurate? anyway As to the copper/brass/bronze "wool"/kitchen scouring scrubber, "Chore Boy" is what ron is talking about (can get them about anywhere and they work great) but make sure it's not a knock-off or unacceptable even if of brand name by checking it with a magnet to make sure it's not just steel shavings coated a bright shiny gold color.