I have hunted and target shot with ITX round balls & shot and they are plenty accurate for hunting. They have been used by other Pro-Staff at Tombob Outdoors to harvest many whitetails and turkey and waterfowl back east. ITX is proven successful in spite of the known issues. I was one of the first people to test ITX in a flintlock traditional longrifle. I found that with the same load, the point of impact was very similar to the point of impact that I was getting with lead roundball at 25 and 50 yards anyway.
I live and hunt in the lead ban zone in CA as well--- actually by 2016 ALL of California will be in a hunting lead ban for all kinds of projectiles including shot. We will still be able to target shoot with lead however--- so far anyway.
I had Rice Barrel Co. cut an extra slow-twist. 1:80 and shallow groove .008 barrel for me to optimize using harder than lead patched roundball. The gun shoots lead and non-lead quite well. I am pleased with it. its a 50 cal 38" swamped barrel in a Jim Chambers Isaac Haines kit.
The biggest challenge for using ITX is the cost, and of course making sure you never dry-ball. Other than that, it is soft enough to not harm your barrel according to the ballistic engineer at TomBob Outdoors, It is accurate enough for hunting purposes, and it is available in the major calibers. I particularly like ITX lead free shot-- it is good stuff especially for cylinder bored smoothies. Have killed several tree rats with it. No turkeys yet but hopefully soon.
Ken
Oakhurst, CA near Yosemite Natl. Park