Probably because I can’t have one here...TBH. :)
Had a CX4 Storm in .40 that was nice. Mags usable in either the carbine or the pistol. Good combo.
Sawing a barrel down and thus reducing ballistic performance for the sake of having a “cool SBR” just doesn’t make sense to me. It’s the counter to having a barrel too long, in which all the powder is burned before your round leaves the barrel. Greatly reduced gas pressures driving the round and vastly increased barrel friction comes into play, and your velocity starts to drop like a rock. I have (and will only buy) 18.5” and 20” barrels on all my 5.56 weapons. I have different parameters for other calibers, but we’re discussing the 5.56.
Velocity is life for the 5.56. it’s too small and light for reduced velocity. What makes it just a good meat ripper is the fact that they travel 3300 ish feet per second, and at only 55 grains, they immediately transfer all their energy, which is pretty immense, into the first thing they hit. At that point they lose ALL their kinetic value, but whatever they contacted is destroyed.
Reducing the speed of a 5.56 doesn’t just make it slower. It transfers much less energy upon impact due to it’s small size and light weight and it becomes a much less efficient round overall.