There has to be a way to use a Dremel tool. Dremel will make everything better.
Slamming the butt against a hard surface while pointing the barrel in a safe direction is a good technique on most ARs but I don't know if the fiberglass will stand up to it.
Slamming the butt against a hard surface while pointing the barrel in a safe direction is a good technique on most ARs but I don't know if the fiberglass will stand up to it.