[willy]

Frank I had the same exact experience with the greatest all around hunting dog anyone in two bird hunting clubs ever saw, his name was Teddy and he was a English Springer Spaniel. If I suggested by eye contact he jump thru fire he would and be happy doing it but he developed a possessive aggressiveness that at first caused him to growl at anyone else that came near something he wanted to chew etc. and that developed into biting my wife on the hand for trying to take a leash away he grabbed and wanted to chew.
I was lucky in that he got a reprieve from the chamber in the last moment by a good friend who had lost his springer two weeks before from old age and he was very familiar with Teddy from training etc. He was a retired fellow that hunted birds every day of the year in three states. He was also a master trainer and there would be no problem with the master/handler situation and he had no one else who would handle the dog, plus the dog would now live in a kennel.
It is traumatic, I have lost dogs for a variety of reason for many years and I remember every retrieve, every look they would give me when I missed the shot and a thousand other memories.
It is part of life and a bond that cannot be quantified, especially for a hunter or other person that works with his dog.
I too have some experience with friends Chessy's and it seemed most of them are a little sharp. I have also seen the same thing in Labs, just not to the same degree and it is much more rare thing.
With each breed generally speaking you have trade offs, and they are all great in my book. Bred to a purpose.
But in the end, taking all of the emotion out of it, they are an animal, a working partner and if they cannot be a responsible member of that relationship then they have to go.
You did the right thing, it's hard, I had to do it three times in my life and I remember every detail. Won't forget and after a time you will remember the great times you had and the big picture will again unfold as that new pup runs across the grass chasing a wind blown leaf.
One bit of advise, somewhere where I have seen the same situation not go so well, give the new guy a fair shot and put more effort into him than you did with your chessy. Don't let the hurt of the last cause any lack of bonding with the new.