If this horse actually had any training by a 'real' reining horse trainer (much less 6 months) and he is 'ripping' the reins out of your hands, something is very, very wrong.
He either has a very bad tooth, is very badly bitted in the wrong bit or is being ridden with faulty techniques. Something is very wrong. May I ask what kind of bit he is in?
If a horse is showing this much resistance, he is far from ready to start on a pattern, even slow. It is not because he can't be guided around the pattern. It is because he has major problems with resistance and you do not want him associating the fights you are getting into with an arena or least of all, the barrel pattern.
You need to figure out why he is 'on the fight' with his bit or with your hands. You need to get him 'soft' and obedient in the bridle and get a willing attitude going with him before you set him up for a future of failure and fights going around the pattern or even going into an arena.
If I am having problems with a horse, we go to the pasture and find a nice, level open place to work it out. I may bring 3 or 4 bridles with me. I may bring 'eyes on the ground' to figure out the problem. But, one thing I do not want is for the horse to get on the muscle or on the fight in an arena. It can carry over into years of problems and a less than willing horse in the arena.
As a matter of fact, we do almost all of our training out of an arena. When we bring a horse back to the barn after a training session, we will go to the arena to 'finish' it. A very brief uncomplicated round or two in the arena, a nice long rest on the far side of the arena finishes the session. Then we get off on the far side, loosen the girth and lead back to the barn. I never have arena sour horses and I never have horses horses that dread a pattern or a place by doing this.
ANY horse that is going to be trained on a barrel pattern should be VERY broke without showing any resistance to lopeing slow and fast circles, loping small and big circles, changing leads and 'checking' from big & fast circles to small and slow circles without dropping a shoulder or throwing their hind ends out of lead.
If you lay a good foundation, you do not have to come back later and try to fix problems.