HELP Mark II Y Horrible groups all of a sudden

[musclecar76]

Well i posted pics but they never got approved. I scrubbed it real good and that ring is still there. Looks like the chamber is separated from the barrel making a little gap where the rifling starts

[Fasteddie01]

Hey Musclecar - I just wanted to come back to this problem of yours. Were you able to get some C-4 or similar Carbon solvent? And do you have or know someone who does have a bore scope? That will show you exactly what's going on inside the bore/chamber. I found a couple threads about carbon rings by searching i-net, too. There are differing views on what/how it builds up, and how to remove it. Here's one - htt p://www.rimfireaccuracy.com/Forums/showthread.php/9488-Carbon-Ring!!
As I said, I use the C-4 letting a wet patch soak for overnite or at least a few hours. An alternative would be to use something like Remington 40-X Bore Cleaner or JB Bore paste on a tight patch, and spun in the chamber on a drill. I did that before I got onto C-4. Using a bore paste pushed thru the barrel (Not Drill) can smooth the barrel similar to lapping. Here's a thread to that effect - see Post #20 - http s://benchrest.com/showthread.php?97313-Rimfire-Cleaning-Is-Brushing-Bore-Absolutely-Necessary/page2& - If you read the whole thread you'll see the different opinions on this, but I think it's a 'real problem' and proper cleaning can solve it. Just using a brass brush and #9 may not be the answer.
Hope some of this can help you,
Ed

[Fasteddie01]

Back again You said that you 'scrubbed' and the ring was still there. Is it something like this pic? It's from my .223 Ruger but I had similar rings on my .22s before cleaning. Using the C-4 cleared them up and I've done the same to the Ruger now. I used to use a brass brush in the chamber, on a drill, but I've read that doing so creates too much wear and can increase the Leade jump to the rifling.
I have a Teslong borescope - about $70 CDN) from amazon.ca. Here's the page from amazon.com - http s://www.amazon.com/s?k=teslong+rifle+borescope&crid=1U8U2EJ9WME3I&spr efix=teslong%2Caps%2C179&ref=nb_sb_ss_ac-a-p_6_7
Pics of Ruger "ring
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