You might try using an 18-22 mm sheep casing. They tend to be very tender and may tear more than you would prefer but they still will give you a nice snap. This size is about 5/8" to 3/4" when stuffed. The sheep casings are halal and Kosher.

Joe Hell - You must have one HELL of a job to feed that 460.

I do. Large, clean chunks of frozen fat, roughly ground muscle meat, wine mulled with warm spices, and then smoked over juniper branches is traditional. I like a traditional salami spices mix to the meat. Make like your favorite salami, about 2" to 2½" diameter casing.

I think you just got them too hot too quickly.