Phew. I had to take some deep breaths before replying to this. OP, just a warning, there is a lot of mis-information in this thread, so read things with a grain of salt.
As i've said before - I never understand why people insist on gameing in shanked bits.
Gameing is a high adrenalin sport - things go wrong, things fall apart at speed that work fine slower. There will always be a time when you need to pick up on a direct rein, hard.
A curb is designed to be ridden on a loose rein
, and neck reined, not direct reined
You can never ensure that will happen when gameing. Even the most experienced horses need a pick up every now and then - Actually my experienced horse needs it more because he knows all the tricks and tries to get lazy by dropping his shoulder :]
So I have started gaming with my horse. I first used a snaffle, but he was not very responsive, so I switched to a kimberwick ( I have no other bits).He is fine unless he is grumpy, which happens quite a bit, then he puts his head down and bucks. I try to pull his head up but it doesn't work. I don't want a harsher bit, but one that encourages him to keep his head up.
Does anyone have any recommendations?
I'll give you some generic reccomendations, but I would like to know - How was he unresponsive? He didn't want to turn, or didn't want to stop? Or he wouldn't rate? Or he was dropping a shoulder?
Once I know that I can give a better answer.
Personally, I only ever game in a snaffle. A snaffle is completely neutral when not being touched. It is very easy to neck rein in a snaffle - Neck reining doesn't involve the bit, so it isn't exclusive to curb bits. It sends a clear, easy to understand signal when you need to pick up on a direct rein to emphasise a turn or lift a shoulder, and it releases immediately. It has good lateral pressure and only applies the amount of pressure on the mouth that you apply on the reins.
Once I know what the 'unresponsive' issue was I can give you tips on how I would fix it, in a snaffle.
So why don't I like seeing leverage bits on a gamein horse?
Well firstly - What is a leverage bit for? Refinement. The curb bit is created so that you can aid your horse with a flex of a finger and the shank allows that tiny signal to be transmitted to the mouth. Even the weight of the reins become a signal. It is very subtle - That is how reiners and WP horses go round without any visible cueing from the rider.
What is the bit NOT designed for? The curb bit isn't designed for direct contact OR direct reining. If you think about the mechanics of it, you can see why. I'll use a solid mouth curb for my examples, but a jointed curb is simlar, just more confusing as there is play side to side in the mouthpiece.
So, direct contact in a curb. The shanks on a curb multiply pressure - So the amount of pressure you put on the reins is multiplied in the mouth. In a snaffle, you can hold the reins in a light contact with the mouth, and you are able to feel the muth but at the same time keep the contact light enough not to influence it. if you tried to do the same in a curb - It wouldn't work. To feel the mouth you have to have a direct line from hand to bit - To do this in a curb the shanks will be fully engaged, which is putting a LOT of pressure on the mouth, poll and chin, even though it doesn't feel like much on the rein. The beauty of leverage. To have the bit sitting neutral in the mouth, the shanks must not be engaged, which means no direct contact.
Now imagine being in a game, and needing to quickly rate your horse to avoid hitting your pocket wrong? You are pumped full of adrenalin, you only have a split second to react - You are going to pull up pretty hard on those reins to ensure a response. Multiply that by whatever ratio depending on the length of the shanks, and that is a LOT of pressure that you can't accurately guage from the reins.
Direct reining - Again, doesn't work in a curb. There are two ways to direct rein - With an open rein, freeing the shoulder to move into the empty space, and a closed rein, to ask the horse to bend around a corner. Neither one works in a curb.
Imagine an open rein - You move your hand out to the side and apply pressure. Now think about a shanked bit - the rein connects at the bottom of the shank, so pulling the rein outward is going to pull the bottom of the shank outward, which will tip the top of the shank inward, and tip the mouthpiece of the bit down on the opposite side. It actually pushes the horses head the opposite direction from the open rein, because of the top of the shank tipping into the head, and the opposite side of the mouthpiece tipping down onto the bars of the mouth. Whereas an open rein on the snaffle pulles the bit straight through the mouth, pushing the head over from the opposite side - Especially if using a full cheek or D ring.
A closed direct rein? Well, the mouthpiece is solid, so it pulls the bottom of the shank back and up, which then tips the opposite shank the same way through the pithpiece - So it then becomes a cue to stop, as both shanks are engaged. The shanks don't pull the mouthpiece toward you, they rotate the mouthpiece and pull up in the mouth and contrict the chin due to the curb chain. Again - not a very clear signal, compare to a snaffle - Which pulls one side directly back onto the bars of the mouth.
Once I know what isues you were hvaing I can give you some ideas on maybe fixing it. All my gameing horses run in snaffle - And my best gameing horse won our zone championships 5 years in a row, undefeated - in a snaffle.