Necro updating this thread but it is useful info.
I did a search all over online and found there were quite a few people having trouble with VFC M4's ridiculously tight outer barrel nut on some of it's models. I wanted to update this thread since it's been Google Search indexed so other people may find this in the future. I have seen some people almost strip or completely destroy their VFC barrel nut. Other branded M4 AEG are a lot easier to just twist it off but VFC has some glue or locktite that makes it hard to twist off without using Acetone.
The Best Way To Remove VFC Outer Barrel Nut
Use Acetone (nail polish remover). Take the liquid and pour it all around the inside of the barrel nut. Let it sit for a few seconds. Then using a Vise Grip Wrench you should be able to turn and twist it off a lot easier. If it is still stuck pour in some more Acetone.
Without the acetone it will be incredibly hard to twist it off. You may end up damaging your upper receiver. The acetone made it super easy to twist off.
