My 4 month old lab?

Just persevere with it, my two Labs were the same, but they did get used to it. It helped to stop them from pulling and they no longer need to use it anymore.

Many people think that gentle leaders and haltis are good training devices and help with control. I personally think they're barbaric. Of course your dog will hate being led around by the face and if he is actually suffering injury, there's no question that it's got to go. This is not the way to gain control, anyway. If your dog pulls when you walk, simply stop walking until he comes to a full halt. Then call him back to your side. Have him sit. Praise him, and start walking again. He can be free to roam and sniff, which is natural, but when the walk stops everytime he pulls, he will learn that pulling literally gets him nowhere. It will take some repetition but it will work. Also, buy some small yummy dog treats. Have him sit by your side. If your'e right handed, seat the dog on your left side. Show him the treat in front of his nose and take a few steps forward so that he is actually walking at your side. When he takes ten steps or so, reward him with an enthuastic "yes!" and treat him. A dog usually walk his owner when he doesn't see his owner as the alpha of the pack. If big dogs can be humanely trained not to pull, there is no reason that a dog of lesser strength should be led around by the face to gain control - which, as you can see, doesn't work anyway. Ditch that Gentle Leader. They're barbaric. A word for anyone else who might be reading this, if you put such a device on a herding dog, this is unnatural to him, as he depends on his eyesight, and you will create a monster. These devices should be illegal.

Do you leave it on the dog all of the time? If not, I'd leave it on him 24/7. He will eventually stop the nonsense, then you can probably take it on and off at will without the fuss. My in-laws dog did this early on, so they just left it on the dog. It flailed around for a while on and off, then it gave up, and they've never had a problem since.

(Obviously, make sure it won't get caught on anything, etc.)

My Lab did the same thing, and I tried for a month.

I found a trainer that taught clicker (positive reinforcement) and it worked wonders. I have a perfect angel now.

have you tried a "harness" type collar? dogs tend to pull less and it isn't around his neck which may make him feel better and less threatened.

my Scottie was doing the same thing. so i got a harness for her it helps you keep better control

Its natural, my dog did the same.