A handguard system for use on a rifle having a barrel attached to a receiver by a barrel nut, including an adapter ring and a tubular handguard. The adapter ring is receivable about a barrel nut and changeable between a rotatable configuration where it is rotatably about the barrel nut, and a fixed configuration...http://www.google.ca/patents/US6671990?utm_source=gb-gplus-sharePatent US6671990 - Rifle handguard system with single end attachment
