well the most scary ride i'd been on in a few years, was an older barrel horse mare, who had been lame, and I was tring her out with the vets permission to see if she was truely sound. Her walk and trot were fine, got her really calm in them even, so we advanced on. I was prepared for her to bolt, and wanted to give her the chance to calm down on her own, so I was out in a 100 acre field, we walked, troted, then I asked her to lope. I heard a great loud pop from her hindquarters and she went bucking/galloping thru the field. Fortunalty she was pretty smooth,but I was still occionally looking for a good place to land if I need/had to jump off. I had a very strong bit (the bit her owners used on her) and I still could not get her stopped.. Finally I just calmly talked to her and got her head pulled around, and she stopped,poor thing was scared to pieces and was shaking! Well come to find out, she was only sound at a walk and trot,her barrel racing days were over. It was sad.she had loads of want to and potential.