What do you mean by "lower twist rates" A 1:7 is a lower number, but it twists the bullet faster. A 1:12 is a higher number, but is a slower twist. Generally speaking lower numbers, meaning faster twist shoot heavier bullets better. Most AR's are 1:7, 1:8, or 1:9 and are meant for 55 gr and up bullets. Most bolt rifles are 1:12 or similar and don't shoot well with bullets heavier than about 55 gr.
I assume you are looking for a bolt rifle with a twist simlar to the 1:7 or 1:8 twists common on AR's. If so, I'm not sure. You could consider buying an AR if you want to shoot heavier bullets. Cost isn't than much more for AR's now and they will shoot just as well as most bolt rifles. It might be the easiest way to get a fast twist 223.