What do you think would happen if the pistol was reassembled without the recoil spring assembly and a round got chambered and fired?
It does take a little finagling, but an M&P can be reassembled without the RSA. However, it won't work like that.
Without the RSA, the striker will push the slide back out of battery once it engages the sear. So, in order to fire the gun, the slide would have to be held forward. Anyone would notice something wrong. Firing the gun in this condition would require a "dare" type scenario and only those from "*******" would attempt something like that. I wouldn't put that past a couple of 20 year olds.
Even if it were fired in this condition, the slide would not come off. Look at this pic:
I made this pic to show the slide contact points. Ignore the green arrow for now.
As the red arrows indicate, there are 4 points of direct contact between the frame (actually the trigger block and sear block which are inserted into the frame and held in by pins through a steel sub-frame) and slide. These contact points are steel.
As the slide travels rearward, this part (red arrow), sometimes called a dust cover, will contact the frame which halts rearward movement. Because of the geometry of the slide dust cover to frame contact, there is almost no upward force; the force is straight back.
Also, as the slide moves backward, the barrel tilts down and the barrel lug engages the slot in the trigger block. Should the dust cover break, the barrel would still hold the slide in place due to the barrel lug.
For the slide to come off the gun:
- It will have to overcome the inertia of the RSA.
- All four of the steel slide rail contact points would have to fail.
- The dust cover would have to break off or the frame fail at that contact point.
- The slide would have to break where the barrel muzzle protrudes through the slide.
- The barrel lug or trigger block (or both) would have to fail.
All of these things would have to fail for the slide to come off. Then, even if all this did fail, all these parts breaking would absorb most of the momentum of the slide. There wouldn't be enough energy left for the slide to "fly" anywhere. It would most likely just tumble off to the side and land on the ground.
A more likely story would be an over pressure round caused a piece of plastic or brass to hit the kid in the forehead. Even more likely is the kids were goofing around and accidentally hit themselves with the gun. Of course we all know that grand parents all have perfect grand children who never lie and are all model citizens.
