I have searched high an low on here to see if there is anything about what fore-end will work with a Sun Devil upper. If anyone has any photos or info of what works and what does not, I would appreciate the input.
FYI... I am looking into building my own custom ground up M4.
Can you be a little more specific on what you are looking for? Are you talking about a Handguard/Rail System? If so, what length gas system will you have? Does the Sun Devil upper have a Delta Ring or a Front Sight Post? If so, do you intend to remove them?