The free length of the Sig spring is quite a bit longer than the Ti-Rant 45 spring (2.025" vs 1.25"). Unless they are compressing the heck out the issue spring, the Ti-Rant spring would just flop to and fro in the Sig piston housing. The Ti-Rant 45 spring is the largest Nielsen Device spring we currently carry in inventory. I'm sorry Apollo, but it doesn't look like I have anything that will help you out.
Mike Smith/AAC
Silent Mike
Mike Smith/AAC
Silent Mike