I find it hilarious that harsh bits are associated with gaming - I am as game to graduate to curb as the next person, but I firmly believe you SHOULD game in a snaffle. I don't care how well trained your barrel racer is, I see SO few pics of them actually NECK reining these horses as opposed to cranking the shank sideways in some mutated yank. For high speed precision like that, I want to be able to haul up my reins and give that fine tuned nose tip where it needs to be. I don't think there's any other explanation for me and Shay-la waltzing into the ring and robbing so many ribbons on completely untrained horses in matching french link snaffles! And in youth, the young lady riding her Arab English swept away most of the competition - his cues were so refined from being an English pony, she didn't waste any time with runaways or not being able to stop him! It's VERY rare I EVER see a horse being ridden correctly in a curb, especially in a gaming ring.
Jynx is going in a D-ring french link snaffle right now, and it's where she'll stay until her neck reining and the rest of her cues are top notch. Really, I haven't graduated many horses to curbs over the years, between my yo-yoing between English and Western, and not really showing, snaffles have always suited my purpose.