We are not sure if you can called the thickened tip (we might have exaggerated it a bit) of the barrel a muzzle brake. A muzzle brake or recoil compensator is a device connected to the muzzle of a cannon that redirects propellant gases to counter recoil and unwanted rising of the barrel during rapid fire. We do not see any features of a muzzle brake on that gun barrel tip... we can only guess it was part of the original barrel design.
With references to the Squadron Armor #20 T-34 in action book, almost all drawings of the T-34/76 models had that bored tip. In fact, on the same publication, a lot of the T-34s photos had that thin outline at the tip of their gun barrels. Because they are B/W picture and the contrast is not the best, but still you can see that feature faintly! This is also why we have put it onto our model. Removing the feature is easy by sanding it down, but adding it back takes extra skill; that's why we have leave it on there!