Barrel question, SR22p

[facn650]

I have an SR22p that has about 600 rounds through it. I first shot a brick of Federal 525 36gr copper plated and it shot great. I then shot a 50 pack of blazer and the groups went to hell.
Upon stripping it for cleaning I noticed a patch getting a bit stuck towards the end of the barrel. I took a look with flashlight and it had some pretty big lead deposits. I had to scrub it and I still didn't get it completely smooth.
This maded me paranoid about my 22/45, 10/22 and my CZ Ultralux so I promptly too a peek down the barrel of those. They all look good and even the 22/45 that has 6k+ rounds and has only seen patches(never brushed) looks pristine.
What could be the cause for this?

[facn650]

Here are some picture, all taken from the muzzle end. The deposits are about 1 inch from the end of the barrel.

[1spartan]

Nasty! I've never seen deposits like that. Am I seeing that correctly? a deposit localized in the shape of a ring?

[facn650]

Yes it looked like a ring.

I ended up soaking the barrel with solvent and running a bronze brush down the bore many times. A bunch of long, thin slivers of lead came out the barrel. It's now fully clean and I'll be shooting it again today and see how it looks after a few hundred rounds. I'll be sticking to the copper washed ammo for now.

I think this is standard buildup, but I wasn't expecting it so soon since I've never had to bronze brush any of my other .22's before, even after thousands of rounds.

[Ron-Solo]

I only shoot the copper washed rounds.

[thrillhouse700]

Does it have octagonal rifling? I can't quite tell from the pics. Only reason I ask is because in glocks they say if you use lead bullets it causes leading and then blows up.

[facn650]

Not sure if octagonal or not.

I've put about 700 rounds of copper washed ammo after the cleaning and it looks good. Sticking to copper washed on this pistol.