If there is a muzzlebreak in the tubes (remember lads, tubes, not barrels) then I suggest that it's drawn in the more "reduced" way as Klaglds suggested. But neither 85mm nor the 100mm tankgun tubes didn't have any muzzlebreaks.
Then It have been a stain on the photo I got. When the upload are, I'll send they wit out that stuff. But thanks for the comments! It helps!