Why is it fine for shotgun shells to be made of plastic but polymer casings for rifle cartridges are considered “unreliable” or “bad” ?

Question

I’ve never fired/handled guns but have some knowledge of guns and their basic mechanisms, and this thought just came across. If you could make cartridges out of polymer/plastic, and they are significantly lighter, wouldn’t you want to switch to them asap? yet there is no adoption. On the other hand shotgun shells have always been plastic but it’s not problematic in any way? why is this the case?

In: 24

Answer 1

It has to do with where the explosion occurs.

In a rifle shell, the explosion happens in the brass casing itself which then forces the bullet down the rifle barrel and out to the target. Basically the entire brass casing holds the powder charge to propel the bullet.

Shotgun shells work similarly, the plastic casing holds the buckshot or lead slug, while the little brass bit on the bottom holds the powered charge where the explosion occurs. Incidentally the smaller powder charge is one of the reasons why shotguns are considered “close range weapons”

While yes it is possible to design polymer casings to handles the explosive material and the heat generated, it can cause a whole lot more problems for the weapon itself.

Essentially; if it ain’t broke, don’t fix it.