So I have been running about 15 HH tall horses if not a little taller and don't have a problem with running or riding them. But my 16.2 HH tall ex racehorse is a challenge for me. My other ones are super responsive to what I ask of them. They rate super good when I sit and my racehorse dude is a PUSH STYLE like nooooo other. It takes everything I have to ride him because he is so big. He is my big gentle giant I call him. LOL. But I need some advice on drills and all to help. He is a 4 year old AQHA. He is way better with speed when going around the barrels. He has the speed in between so that is not an issue its just the turning. With the bigger horses do you guys try to push them by the barrel then come around? I try to push him by it but I am so use to sitting on my others that we turn too soon and have no moumentum going around the barrels. I have him in the million dollar bit by Martha josey.  He does bend but when going around the barrel I can't seem to hold him up to help him stay correct. I work him in rings every now and then. He is extremley hard to push by plus to get him to keep his shoulder up.. I would love drills for the big guy. And other bit reccomendations. He is just so so so big its hard for him to do tiny circles all day it seems. We work on flexing and bending daily. 

P.s I have thoroughbreds so I am familiar with racehorses just not putting them on the barrels. ;)

I do squares instead of circles, works for taller and shorter. Helps them figure out how to use their body more upright while making the points of a turn. Sharon Camarillo teaches it, I believe Danyelle Campbell does similar with her horses too & a few others that I can't think of their names. Its a good exercise to work on one keeping their shoulder up & their butt under them. My mare is only 16h and she doesn't do small circles well, but she has no problem doing the small squares. I've found sometimes larger horses don't do as well with just a simple circle turning style, they seem to do better with points of a turn, like Ron Ralls method for example. A more squared approach. But thats just what I've found. & all ottb's I've seen start a pattern are the definition of push style, they're exhausting to run 

My gelding, now retired was 16.2 and very ratey. I think rate points/basics are the same on 14.h bs 17h. I made sure to ride my horse until my leg was past the barrel and when I say ride him, I mean it. 2 handed, square and acting like we are going to the fence. As soon soon my leg was by then I looked and he snapped around. As far as drills, I practicied a lot of drills doing the barrels but all rights or all lefts Example, 2nd barrel...3rd barrel.. back to 1st (if you horse is a righty). I make sure to keep a consistent 4-6 feet around the whole barrel to keep him collected but not diving into things. 

As far as bits, I wouldnt have a super ratey/horse in a million dollar. Just seems like a lot. Bit is only as bad as your hands but sometimes that type of leverage can really clam a horse up. Without knowing your horses, hard to recommend much. But I usually go into something like a Charmayne James Ryan after snaffle, tender touch or Jr cowhorse. My mare runs in the Futurity Bit by Prof Choice and she is also very ratey and prob could run her in a halter. 

Video would help too :) 

First of all they need to be extremely well broke. All of mine are 16 to 16-2. They are so broke I ride them in trail horse classes. Horse needs to be up in the bit, rounded back, with feet under him. Roll backs are not the best way to get one’s feet up under them, especially a big horse. Tried to post a video of my 16-2 mare but can’t get it to post. My trainer usually rides her and when she rides her everyday she just works on basis I think she may breeze her through once a week.

I have the opposite problem lol! I cant get with smaller horses.. I LOVE um big and tall. That's probably because I grew up on warmbloods in the hunter jumper world. I just sold a horse we had for a while because I couldn't get over how small he was, plus I didnt enjoy riding him, he felt like a pony! 

https://youtu.be/e7eE6N8Sxx0    Don’t know if this will work. This horse is 16-2. This is her run at the AQHA WORLD SHOW. I am not the person riding. I am the maniac yelling in the background!

I am the opposite because I seem to do better with the big horses, haha.

Of course every horse is unique in how they run, but for the bigger horses I have run, you really need to make sure you get them deep enough in the pocket before starting your turn, because they need the room to get their body around.

I also feel like the big horses are more "forgiving". They usually have a pretty large stride which can make up for it if your timing is off. I also started riding a little horse (about 14.2 to 14.3 hands) that is a quick little guy and man, I usually sent him too deep into the turn because I am just so used to running my big guys and not used to how QUICK he responded.

I might be a little weird in that I don't like my horses to lope a western-pleasure speed turn around the barrel and can keep doing it endlessly. I see lots of other people able to do that with their horses, and honestly a bit jealous at times that mine don't do that, but I also just personally do not like making them go around that barrel endlessly, so if they complete the turn correctly and use their body correctly, I guess it doesn't matter to me that they didn't do it super slow.

I am personally not a fan of the Million Dollar Bit. I think it's a lot of bit with a lot of things going on. I can't imagine using something like that on a 4-yr-old but that is just my opinion. I like my horses to be able to do other things than barrels, and it's really important to me to have them broke, broke, broke in a somewhat light bit.

If you are having trouble keeping his shoulder up, and other general riding problems, seriously don't worry about the barrel turn. Quit working the pattern for a while and just work on making him BROKE. Be able to lift the shoulders, ask for a correct lead departure (from a walk or stop), bend the ribcage, break at the poll, etc etc etc. Get him really responsive to all your cues and be able to control any part of his body. Then at a later time, go back to the barrel pattern. If you;ve taught him the basics away from the pattern, it is very easy to apply it to the pattern and you'll have much less trouble.

I also have never been much of a drills person; I just get too bored working patterns. I prefer to focus on just getting them broke broke broke, either inside the arena or outside the arena.

My thing in reading your post is, he's only four.. how long has he been off the track? I have trained a few OTTB's and I had a put a good 6-8 months of solid foundation training before even thinking about putting him on barrels. I mean, really putting all the bells and whistles because for one.. they needed to be retrained. They had no idea where to put their feet, how to collect, how to bend, or flex, or get their hind quarter's under them, give to the bit, pick up the bit, side passing, reverse arcs etc. 

I don't know the horse, but maybe give him something else to do? I wouldn't be putting him in the million-dollar bit either.. that's a pretty hefty bit, I agree with the possibility of the CJ Ryan Bit.. I love that bit and have never met a horse that didn't like it. Can I ask why you have a combo on him? Maybe put something on him to help free him up. Something softer, lighter. If you say it is difficult for him to make those tight turns, then most likely he needs to build his strength to hold those turns which will take some additional conditioning. Horses are not designed to make those tight turns, they need to build up the strength to make them or else they will break gait.