I come from a competion background, so I like a steady dog. If one likes a dog to be there when the bird hits the ground, then just work on sit (a side note, pointing dog people like the dog there because the dogs don't mark as well or have the desire to trail cripples like a spaniel or a retriever). Teach the dog to sit, no matter what!!!!!! When you blow the whistle, his butt hits the ground, period. There could be a bitch in heat, whistle, sit.
How to do it without beat the s**t out of the dog? Sit the dog on a mat, board, or whatever. Hook a check cord on the dog. Walk a few yards off. The dog is on sit, so pull on the check cord. When the dog moves the first time, correct him and put him back on the board, mat whatever you use so he knows he moved. When you can't pull him (let's be reasonable, I weigh 275, I can pull a 100lb Chess the lenghth of any check cord, use wisdom) off the mat, board whatever, you are maybe close to being started. Do this with voice and whistle. I know you haven't done this because your dog isn't convinced you mean sit. With the check cord still attached firmly to the dog, move to the field, WITH NO BIRDS!!!!!!!!!!!!!! As he is messing around blow the sit whistle. When he doesn't comply, discipline him (yell NO, e-collar a message, whatever to get his attention). Put him where he screwed up on sit, praise him, and do the check cord pull again. Do this until he sits every time. He doesn't do this because he ignores your whistles. Finally intro birds into the epuation by using clips thrown in front of him and blow the whistle. Correct him when he screws up (sounds like a broken record). You now have his attention. He should listen to you when you whistle. Correct him when he screws up. This works. A springer wants to please you. I used the same technique with a Jagdterrier. They as independant as a hound, with the inteligence of a chimp. He wasn't trained or socialized when I bought him at 2 1/2 but he is buying what I'm selling now. He didn't care if he pleased me but we worked through that. I can get him to sit when I say sit now.
Dr Fatguy