It may have a detrimental effect on achieving top accuracy that the rest of the rifle is capable of:
Being not vented, the moment the bullet leaves the barrel, the swirling gasses aren't free to just expand in every direction (like a typical hunting barrel), they aren't free to expand in certain directions (like a proper flash hider), they aren't shunted off axis and slowed cooled (like a sound suppressor)...no, they are contained and reflected off a tight cylindrical surface for another 3 inches. Any turbulence in this expanding gas could throw the bullet off slightly.
I'm not talking a big difference in accuracy here...it might not even be noticeable under 300m. But if you plan on competing at 500m, or just want the best the rifle has to offer, either remove it or replace it with a proper one.
Think about it this way: match grade or precision rifles have the muzzle crowned very precisely, so that the gases are released perfectly all around the edge of the bullet, not venting on one side before the bullet is gone from the gases. Well, these old Chinese non-vented fakes, is like putting the absolute WORST muzzle geometry you could possibly put on a rifle!
I replaced mine for that reason...and also because the proper one actually looks a lot better IMO. And got help putting it on, thanks Thomas!
I should add: I replaced mine with a Chinese proper vented flash hider, that way it didn't cost much for the part.
