Originally Posted by smrobs
One thing that he didn't mention is that you'll actually want to take the measurement between the marks and add about 1/2 inch (1.27 cm) to it, especially on a bit like a loose ring snaffle. That way, the bit will be wide enough that it won't pinch the lips or face.
If you buy a bit that is exactly the width of the horse's mouth, then a loose ring snaffle will pinch and sore the corners of the mouth. You could probably get away with it if you're using an eggbutt or a full cheek, but not many other bits would be as forgiving. If you buy a curb bit the exact width, then the purchase rings will actually dig into the sides of the horse's face because their face gets wider just above their lips.
Most horses that comfortably wear a 5" bit will actually have a mouth measurement of ~4.5".
Good to know, thank you smrobs. I was thinking of getting a french link snaffle. Do you think that is a good bit that isn't too harsh? Or is there a different type of snaffle you would suggest? I never knew there were so many different types of snaffles. I know nothing about bits, so I've been trying to do a lot of research. In the end I'm normally confused.
Oh yeah, the bit is for my 17 year old gelding who normally has a lot of go. He's been using Martha Josey's Million Dollar Bit but without the rope over his nose. That's what was recommended to me by his previous owner, but honestly, I don't really like it and I don't think he cares for it either.