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

As everyone said the pressure difference is massive. But the effective range is also extremely different. The effective range of a shotgun with buckshot (large pellets) is only 35m, birdshot (small pellets) is 45m. Where as a 62 grain 5.56 maximum effective range is 600m to 1000m. So you need a LOT more pressure to push the round at that speed.