Exactly. There is a wide spread of different plastic materials and the one used for the Pandora was very weak and brittle. Today, even guns can have an huge ammount of plastic parts, we had the (back then) new G36 in our Army time for a short while at the end and this thing was basicly almost entirely plastic in the case parts. Very hard, very durable stuff, surely polymer/fibre enhanced. Even the transparent Magazines were plastic. Actualy impressive if you know the forces that can happen within a real rifle.Well, there are hundreds of different plastics available. Some softer, some more brittle.
And the cheapest ones are very brittle, as they're mixtures of different kinds of plastic (probably whatever is left), they break easily.
"Plastics" does not mean weak at all. There are several polymers that have better properties than metal in specific areas (tensile strength, bulk strength, see GRP for example) and they are used even in stuff like planes where metal alloys are too heavy to be used. There's a very wide range of artifical polymers and giving it a single name does not do it justice.Actualy impressive if you know the forces that can happen within a real rifle.