[Eghad]

http://www.ar15armory.com/forums/AR1...Tec-t5332.html

To see if you have a short stroking problem and not a “Failure to Feed” problem, please perform this test first (assuming your bolt catch and magazine is functioning properly). Insert one round into a magazine that you know to be performing well. Insert the magazine into the magazine well, pull the charging handle to the rear, then release the charging to load the round into the chamber. Safely discharge that round. After the round has been fired the bolt should automatically be locked to the rear by the bolt catch and the empty magazine. If the bolt is closed on the empty chamber, then it did not travel far enough to the rear to be held by the bolt catch, and your rifle has short stroked.
Short stroking is a symptom of a problem with the gas system in the rifle. There are 7 parts of the AR gas system. In the upper receiver group, you have the barrel (gas port), front sight base, and gas tube. In the bolt carrier group you have the gas key, the carrier, the bolt, and the gas rings.