Glock 22 barrel issue

[Jericho9]

I was cleaning my glock 22 and found this in the barrel and it's not coming off. It shoots fine. No FTF or FTE. Just curious what it is and what caused it.
Thanks guys

[Condorguns]

What ammo?

[Jericho9]

Aluminum federal. But Iv put same ammo through my old glock 22 gen 3 and barrel was clean after wards . No marks

[Cali-Shooter]

Won't scrub off you say? Is that simply discoloration, stripping of finish, or is it actually some sort of substance/residue? It's hard to tell from your picture.

[Oceanbob]

Dry aluminum and on the ramp, that cheap copper coating Blazer dips the boolet in .......

[Jericho9]

Won't scrub off you say? Is that simply discoloration, stripping of finish, or is it actually some sort of substance/residue? It's hard to tell from your picture.

Yeah won't scrub off. I'm guessung it's stripping of coating but that's never happened to any of my glocks. But I'm not 100% sure

[maulich]

Try some hopps foaming bore cleaner on it. Should take it off.

[Jericho9]

Try some hopps foaming bore cleaner on it. Should take it off.

Thanks dude.

[Leagle8]

Yep a good bore cleaning solution and elbow grease.