Hk45USP, I have seen the receiver of an M16 crack. In all fairness it was an older model that had been fired no telling how many times. I am sure it would have cracked at some point regardless of what it was machined from.

On the the whole "lightweight" shotgun thing. I personally do not like to feel pain when I pull the trigger. The lighter the gun, the more felt recoil. I also prefer a heavier gun for shooting since I feel more stable.