I am in agreement about the plastic (the ones currently on the market are made of either polycarbonate or nylon) not being up to adequately handling the extreme forces that it has to endure. There are currently 4 manufacturers that make them, but the ONLY size that is currently available is 22/30 (224/308). At least 1 of them does make a 30/50, but it is also unavailable, probably due to massive purchase orders being placed by the military. I think at least 2 of them say they are planning on offering other sizes, such as 22/7mm, 243/7mm (that's the one that I'M waiting for), 243/30, 22/270, 243/270, 338/45, and 338/50. It makes sense to me that the smaller the difference in caliber (less side thickness of the sabot), the less chance there is that the issues mentioned will manifest themselves. The wait for the additional sizes is getting very long indeed, as they have been saying that they will be coming out with them for quite some time now, but they still aren't available.