Maybe I missed it, but I didn't see anyone mention not to put a plastic folding front sight on a centerfire AR15 railed gas block if yo get the barrel hot enough to not be able to touch it. Use a metal folding sight. The plastic folding front sight is intended to be mounted on a free float forend, not the gas block. The only gas block I put a plastic folding sight on is on my .22 LR AR, as it will never get hot enough to cause a problem.