I personally always use Delrin but there was some concern posted about the Delrin getting "rubbery" with high temps and brittle with low temps. I personally never had a Delrin failure but I thought I'd check out the service temp anyway and here is a screen shot from McMaster Carr..........
Anywhoo.....minus 20F is a lot colder than I'll ever do any springer shooting and plus 180F is a lot hotter! Perhaps that's why I've never had a Delrin failure!

Anywhoo.....minus 20F is a lot colder than I'll ever do any springer shooting and plus 180F is a lot hotter! Perhaps that's why I've never had a Delrin failure!