Is it going to damage anything if I go to town with a brass brush on my chamber?
I don't know whether it was a dodgy load but have some debris stuck on the inside of my chamber that looks like specs of brass but it could be a burr in the steel. It stops extraction and scratches the hell out of my cases.
If I go to absolute town with an oversize brass brush should be okay, I know steel is harder than the brush but I don't want it made worse!
A good brush should do the trick and shouldn't damage the gun. I doubt its brass as brass itself is a soft metal and wouldn't really scratch your cases.
Finding someone with a borescope might be a good idea too
"it's a Fuster Cluck!"
give a good beating with a phosfur bronze brush and hopefully it will shift it, failing that, as said above give it a poke with a borescope and see whats happening