From nationally known 1911 custom gunsmith Ned Christiansen, who is also a stellar AR-15 ‘smith and operator:
“They’re almost upon us, grab one of these rifles and get ready”: the 30-second prioritized AR15 checklist. Items are prioritized factoring in criticality, ease of checking, sequence and likelihood.
If you have a half a minute, you can confirm that:
1) Hammer and trigger pins are flush to receiver sides and not hanging out. A trigger pin sticking out almost certainly means the hammer spring is improperly installed and is not detenting the trigger pin in place. The result will almost certainly be sporadic or continuous misfires, burst fire, shut-down. A hammer pin sticking out probably just means it was not pushed in far enough. It is detented by the “J” spring, which is simply a length of spring wire that is permanently staked into the hammer. These practically never fail or come loose.
2) Hammer spring is correctly installed with both legs horizontal, spread out against inside wall of receiver, and laying on top of trigger in properly in the at pin’s outboard groove, acting as a detent for same. A hammer spring installed backwards will give a light primer strike causing misfires, and although it may appear to be laying on and detenting the trigger pin, it in fact will not. This will lead to the trigger pin walking out and causing failures to fire, or doubling/burst fire. Hammer springs not installed backwards can still be improperly installed, with legs either under the trigger pin resting on the floor of the receiver, or inboard of the receiver wall and thus not laying in the detention groove of the trigger pin. In either case the above trigger-pin-walking problems will be the eventual result, plus, when the legs are under the trigger pin instead of on top of it, the blow to the firing pin is receded somewhat as the spring is not as “wound up” as it would be when properly installed. …”
To read the remaining steps of Christiansen’s 30-second check as well as other quick checks you can make, purchase Gunsmithing the AR-15 from Gun Tests. You’ll also learn many maintenance, repair and ‘smithing tips from the book.
