Folks, please stop bugging TI about stronger calibers or +P loads for this thing. It is built on some sort of alloy frame, which inherently limits it to lower-pressure cartridges like 410 and standard 45LC.
As far as I’m aware, there are virtually no alloy-frame revolvers designed to handle anything more powerful than 38 Special on a regular basis. And those revolvers are from established manufacturers which use advanced materials and extensive testing to safely push those limits - and that’s not something without clear evidence. So, these fantasy suggestions like 9mm, 357, 44 or other higher pressure rounds (which operate at double the pressure and more) are simply not realistic for this type of frame material.
Bottom line: standard 45LC is the practical upper limit for this design, it's good for what it is. Moving to higher-pressure calibers would require a fundamentally different platform with a steel frame and new price tag. So TI is absolutely right, when they say no other calibers in the works. They never be. Though, shooting 45LC reloads with casted bullets will make it very economical and fun range toy.
And even when the stronger steel frame revolver rifle design would hypothetically come up with hotter calibers - too much hot gas escaping from the cylinder gap toward the shooter’s hands and face will then be a real big issue. That’s another reason we likely won’t see 45-70 or something we are hoping for. And I'm not talking just about Sulun.
Hope it helps.