If you look up the melting point of polyethelene you will find: The brass will burn right through the poly film. Have not tried it with pistol ammo but I have with 5.56.
Lay a piece of polyethylene film out on ground and fire your AR so the brass will impact the film. The 'bump' was added to upper receiver that changed the brass ejection to 2:00 to 4:00 and that helped us lefties but directed 1/3rd more hot cases directly towards shooters to the right. In 1982 the M16A1E1 was tested at Aberdeen Proving Ground and adopted as the M16A2. The early versions would cut small chunks of the right cheek of left hand shooters thus the plastic case deflectors were sometimes available.
The AR platform initially ejected hot cases from 2:00 to 5:00. Want to see how hot brass is just lay out a piece of polyethylene film on the ground and fire your semi automatic rifle in a manner that will deliver a hot case directly onto the film. Hot cases from handguns can be exciting but hot cases from a AR can really be life threatening.
