Help with bit choice

One of my horses is a 16 hh Morgan very forward. To forward lets go! - for me. My trainer has recommended to change his bit. He now has a D ring copper roller snaffle. She said to maybe get a stronger bit to help slow him down. Is this the right thing to do? She said it would help my confidence on him. My other horses Appendix and AQHA also have snaffles and are great on them. Please give me some advice on slowing down a horse that likes speed.

Before upgrading to a stronger bit, it is usually better to try to change the behavior instead of man-handling it with a harsh bit. I would keep him in the bit he is in and work on "cruise control". Lots of small circles at a trot with his head bent slightly to the inside will help. Serpentines are always a good option. Do you ride english or western? Regardless, you may want to try riding him on a loose rein for a while. LOL I know that sounds like it would be the opposite of what you would want to do but I have been doing this on my very chargy QH and it has been working. Start at a walk on a loose rein. When they start to speed up, do a one rein stop. Then start walking again, when they speed up, do a one rein stop the other way. The next time, stop them and back them a few steps. Each time after you stop, allow them to stand for a few seconds before asking for forward motion again. Slowly keep working at this and as you gain control, work your way up to the faster gaits. It will take him a while to get better and he may never get completely over it but doing this will make him much more controllable. Good luck with him. :)

Bits don't fix fast horses, training fixes fast horses.

Lots of trot, rebalancing, half halts, and transitions. There's an exercise I wrote up in another thread re: jumping (I think in the English riding thread) that would apply for you too and likely help.

Thanks I will try your suggestions. He is so collected (on his own) head in and full steam ahead march/bounce that when you ask for a trot or canter he kick starts it and it unnerves me. I ride both English (on him) and Western on my Quarter horse my preference. He is kind and well mannered just loves to go. Should be an endurance horse!

I completely agree. A bit won't make the horse - the training does.

I do have a couple questions though:
- Does the saddle fit? (Horses sometimes will "run" from the pain of an ill-fitting saddle)
- Does the bridle fit?
- Are you using a single joint bit or a double? (Some horses, like mine, have a definite preference for double joint bits)
- Has the dentist been to visit the horse recently?

If it isn't broken don't try to fix it. If your horse is happy with the bit you have keep it. As everyone else has said more schooling . A stronger bit will probably lead to an unhappy horse , and can just be a downward spiral where you keep having to get a stronger and stronger bit untill you have a horse with a hard and un-responsive mouth.

I would like to know what he's eating (grain, hay, supplements) and how much turnout/pasture time he gets. Food and turnout time both greatly effect a horse's energy level and behavior.

If he doesn't get any (or much) feed or grain, little to no Alfalfa hay, and has at least 12 hours of turnout time, then I'd suggest getting some Dressage lessons on him before changing bits. You may just need to learn how to more effectively communicate with him, to help him understand what you want better (slower gaits). Learn to use lighter leg aids, more seat aids, and softer/quieter hands/arms/shoulders to give him a sense of "calm" in the saddle and slow him down with little to no rein pressure.

Another possibility if your horse tends to go behind the bit is that he has a sensitive mouth. You may want to try a happy mouth bit on him. I like the loose ring double jointed happy mouths!! They are great because they are rubber it encourages the horse to take the bit and the double joint lets you isolate one side of the horses mouth at a time which also helps prevent the horse from leaning on the bit or resisting too much.
If it is hard to slow him down you may also want to consider a flash nose band which will also help encourage him to take the bit and not evade it.
I also agree with the idea of anytime he starts to get quick and you ask him nicely to slow down and he chooses not to slow down. . Stopping him and if he's not too sensitive backing him a few steps to correct the behavior. However this only works if you do it EVERY time he has the wrong response to your request. It will most likely be every few steps at first. And if he can't stay calm and slow at the walk make him stay at the walk and use the halts untill he can stay calm and slow.
Its not necessarily wrong to go to a stronger bit however if you are intermediate or more of a beginner rider and do not have an independent hand it may be a good idea to have your trainer ride your horse in the new bit first to see what the horses reaction is.

A bit might not be the problem, but changing it wouldn't hurt. Changing to another snaffle bit would help without being too demanding and challenging. I changed my horse to a full-cheek snaffle with keepers to help.

Training obviously helps, but if that's the only way control would benefit then we wouldn't have so many bit options, I feel.

Did you trainer actually suggest what sort of bit to try on your horse? Im guessing she probably did if she suggested that you try a stronger one...

I agree with some horses prefer other types of bits my girl was in a plain eggbutt snaffle when I got her and she would tank and was generally not happy, same in a double jointed but she loves a mullen mouth.... IN saying that I use another bit for jumping... (Not a harsh one though just one she can't hold). So you may want to try another style bit .... (ie if you are in a single joint try a double or mullen)