painting muzzle brakes?

I guess the only real question here is: Is the German gun that YOU are making in a combat situation or receiving maintenance? Paint your vehicle; muzzle brake included, according to what you want your vehicle to be doing. Good luck. 

I speak as an active duty artilley officer for 23 1/2 years.  Yes, there is carbon in the barrel and around the muzzle, just like any gun will have after firing.  This does not make the muzzle black or stained though, and it is not soot.  The fluid used to clean this carbon can/will slightly discolor (like an oil stain) the muzzle as it is wiped away after cleaning said carbon.  Coloring the muzzle black as many modelers due is not accurate.

I can understand HeavyArty's response, but as someone who called in arty; worked the gun line with the cannon cockers to see what it was all about and shot the M16A1 and still shoot to this day, with all these "smokeless" powders, you will still get carbon deposits and residue after shooting in the barrel, working parts and muzzle brake. And I would be breaking the 'cardinal rule' of every Marine, by not cleaning your weapon after firing. Believe me there is always carbon residue (soot). BTW I never color my muzzle brakes in black. I use a 50/50 mixture of Flat Black/Flat Brown, which I call "Soot". Just my two cents.

   Thank you for your expertise on this question HeavyArty, I humbly stand corrected.

It is an overdone, modeling myth to darken muzzle brakes.  It is not from either powder nor heat.  If hear were the case, the whole barrel would be discolored.  The muzzle brake is not a heat sink either.  It helps w/recoil and muzzle flash.  What you are likely seeing as darkened muzzles is from cleaning fluids used to clean the barrel that discolors it.  

    Even if they used smokeless powder in thier rounds there is still heat to think about. As many rounds are fired the paint and primer would become discolored from all the heat generated by the rate of fire. Muzzle brakes are not only a way to disperse recoil, they are also heatsinks to help cool the tube.