It's downright cruel to let them suffer. If there is no other option a bullet is a blessing to a suffering soul.
This is why I asked this question to begin with. We all love our 4 legged partners, and in my mind I could never see letting one suffer for longer than absolutely necessary.
There have been some awesome discussion on this thread, and I do appreciate that everyone has kept it constructive. It's a terrible issue to think of, but we take these guys into our hearts, homes, barns, and lives. IMHO it is just as important to plan an emergency euthanasia as it is to plan for fire, natural disaster, and emergency services.
As far as the impact on the owners well it isn't something to think lightly of. If you aren't sure where and how to place the shot PLEASE get someone with more experience to do it! One of the poor guys I had to put down was sitting with 3 bullets in his head, bleeding and screaming, and it was the most horrific one I have had to do.
To this day, his owner has never gotten another horse. She was traumatized by the attempt to shoot him and the subsequent failure of her efforts. There are pros and cons for everything in our lives. But the more knowledge we have, the greater our chances of making a decision that we can live with in the event that something goes wrong. It can and does go wrong! I have seen euthanasia go horribly wrong for all kinds of animals. (Former BOD for an animal shelter)
Thank you to everyone, even the caliber discussion group, for thinking and placing more information at other horse owners disposal. The more we learn, think, and discuss, the more our animals benefit.
When you close your mind to alternatives you may be forced to make a decision that you can not live with, after the fact. If I had not called the vet out for one, he'd have been gone a lot faster, and I'd not hear him scream sometimes in my dreams. 3 hours of screaming and thrashing is not something you want to ever have to repeat. Impaction colic can and does often become extremely painful, in a very short time. He was 24 years old. He did nothing in his life to deserve to die like he did. I own a pistol for just this reason. I swore after that episode with my friends old guy, I'd not be without a pistol ever again.
If anyone learned anything from this AWESOME! I hope it got people thinking and planning. Life is short, and it shouldn't be filled with regrets and recriminations for the animals that mean so much to us.