UHMW or HDPE will work just fine. Too, these can be inserted into the primer recess of ctg. cases, but - a better method is to make a 'fake' ctg. out of them for your own snap-cap. The material is the perfect modern horn.
: There are many grades of this stuff - the harder ones ar th ones I'm referring to. Cutting boards usually are the softer varieties. Here, in Canada, UHMW is used for cutting boards in butcher shops. It's quite hard and resilient, much more so than the store-bought boards, which are too soft & used in comercial snap caps. It holds screws well, and has many uses.
: The coloured UHMW is all re-claimed pieces, trimmings put back into the 'pot' and therefore a die is added to identify it. Although it is all brand new 'product' it is not allowed for comercial butchershop cutting boards.
: It turns very nicely on a lathe at high speed, slow feed, which is how these 'snap caps' are made.
; UHMW means "ultra high molecular weight"while HDPE in the States means "high density polyethyline." There are different grades of HDPE I assume. Large plastics shops who pecialize in this stuff usualy have a 'piece bin' that they sell chunks from for the price of some Friday-night beer money.