Nice, but to be honest I don't like the resin "counterweight". I understand that it was made separately to allow for inserting the fume extractor part from the muzzle end, but the way it was done makes the diameter of this counterweight too big. This is a minor flaw, but noticeable for me. In reality the difference in diameter between the barrel and this counterweight is minimal - sometimes even hard to notice in photos. But resin casting limitations meant that the part couldn't be made as thin as it should be to be fully accurate. Much better solution would be to machine a muzzle tip of the barrel to reduce its diameter slightly on the length of the counterweight. This way the fume extractor could still be easily put on the barrel and the counterweight could be of more correct diameter, as the thinner barrel tip would allow for thicker wall of resin part, without making the external diameter too big.
If I decide to buy this barrel, I will replace the resin counterweight with a single layer of Tamiya masking tape around the muzzle end - it should be enough and more in scale thickness. If cut precisely the ends of the tape should meet without any noticeable gap - and it could be placed on the bottom side anyway.