, I think you are referring to the commander versions Les Baer puts out, Comanche and Stinger. I've only read that some guys have those models that won't sling shot. Others have the same models from him and say theirs will do it all day long. I have no first hand experience with them. Can't drop that kind of coin on a single pistol yet.
I do know that by adding a shock buff to some pistols will greatly reduce your ability to sling shot them. There is only so much rearward travel to be had and adding a shock buff eats up that distance.