Is there a reining trainer anywhere near you that can help you? It sound like you are putting too much pressure on him and trying to 'force' a turn-around instead of 'letting' the horse turn around.
Never, never, never back into a turn-around. It is always the wrong thing to do. You need a horse to be 'flat' and not back or too 'deep' behind. A horse can do a 'roll-back' or half of a spin while it is deep behind. It is impossible for a horse to keep going around and around unless it is flat.
The best way I know to 'let' a horse come around correctly is to do small circles with the horse's head 'over-bent' to the inside while the horse is being 'wrapped around the rider's inside leg. The key is to get the bend and the tight circle on a loose rein. You do this by 'bumping' the inside rein when and if the horse tries to straighten his head/neck out and NOT by pulling steady on that inside rein. If you have to pull steady, the horse is putting his energy into NOT BENDING. The idea that you bump him and he makes the tiny tight circles on his own is VERY important.
Then, when the horse is not showing any resistance, is keeping his circle tight and tiny and keeps his nose far to the inside on a loose rein, you take your inside leg off of him and 'LET' him come around. I usually do not even have to put any outside leg on the horse. The horse gradually comes around farther and farther on its own.
You always push a horse forward when you let the horse straighten out.
You will still be better off working with a trainer. Knowledgeable eyes on the ground can tell if a horse is setting the wrong (outside) foot and if the horse has a stiff and resistant spot. Some horses need a 'centered' rider and some horses need a rider to put a little more weight in the outside stirrup. Only eyes on the ground and a 'test ride' by a trainer can tell you what you are doing wrong for sure.
Last edited by Cherie; 10-22-2012 at 10:25 AM.