Are Muzzle Brakes "jaggy" inside?

[marklbucla]

I have a post ban Bushmaster M4 upper with a permanently attached mini-Y comp muzzle brake. The outside of the brake looks fine but I noticed that the muzzle brake has a lot of "jaggies" on the inside and well, to describe it as best as I can, it looks sorta like it's been burned.

Here's the best pic I could take of it. Is it normal or do I have a defective brake?

 

[Jay Kominek]

That is, a, uh, not very helpful picture, I'm afraid.
Are we talking about surface roughness of the metal, or jagged pieces poking out that you could cut flesh on?
I'm not familiar with the mini-Y, but I'd expect that when the brake is machined, they just drill the bore out, rather than using a process that would result in a smooth, pretty looking interior surface. After all, they're just making the hole big enough for the bullet to pass through, as quickly and cheaply as they can.

 

[dfariswheel]

The burned, rough look is probably a coating of carbon and bullet jacket material.

This tends to build up in muzzle devices.

Other areas can actually be eroded by the highly abrasive, super-heated gas and burning powder particles.

This can "bead blast" metal to a rough surface.

 

[Rockstar]

It's carbon build-up. There's a spray, I believe it's "Carter's", that's supposed to mitigate the build-up. I don't use it, so I don't know if it works or not. I've removed carbon from pistol brakes with a Dremel and small sanding disk.