The Gun Digest Book of the AR-15, Volume III - Patrick Sweeney

The Master of the AR-15 has done it again! The AR-15 has become America's favorite rifle-and no one knows it better than Patrick Sweeny. Now, in Gun Digest Book of the AR-15, Volume 3, Sweeney unlocks the mysteries behind the piston AR.
AR Piston designs AR-15 conversions from direct impingement to piston operation New AR manufacturers: H&K, Sun Devil, CMMG, among others AR-15 mags and other accessories
From factory-stock rifles to do-it-yourself conversions, if there's anything you want to know about the latest generation of AR-15s you'll find it in Gun Digest Book of the AR-15, Volume 3. Whether you're buying your first AR or building one from the ground up, there's no better reference than Sweeney's AR series from Gun Digest. And now, with Gun Digest Book of the AR-15, Volume 3, you too, will be an expert on the most popular rifle in America!