I have just built my first Ar-15, first I would like to thank everyone here for all the help and for the information.  It has been very useful.  I have a Rock River lower with a Stag Arms 16in. flattop from Del-ton.  It has been working wonderfully for about 2 weeks.  Then one day I was firing it, it decided to shoot 2 rounds with one pull of the trigger.  It was in the middle of a magazine and I was not able to replicate the problem.  Since my range is right next to the police academy it had me a little worried that the report might attract some unwanted attention.  Has anyone else had this happen to them?  

Field strip the bolt and carrier and clean thoroughly and test it out.  If it happens again, remove the FCG and call whoever you pruchased it from and ask if maybe theyll replace it.  

I will have to try that this weekend.  I usualy keep my stuff in clean working order, so hopefuly it was a one time thing.

If you are having multiple rounds fired with one pull of the trigger the timing of the disconnector, trigger and hammer is the FIRST place to look. Charles the Gunsmith.

Quoted: If you are having multiple rounds fired with one pull of the trigger the timing of the disconnector, trigger and hammer is the FIRST place to look. Charles the Gunsmith.

What he says,  should take you no more than 15 minute to remedy, with no replacement parts... been 15yr now with mine.  

Reset the disconnect timing/engagement.

I am kind of new at this, how would I go about reseting the disconnect timing/engagement?

Quoted: I am kind of new at this, how would I go about reseting the disconnect timing/engagement?

You will first seperate the upper from the lower (std warning--> be sure the firearm is unloaded/safe)

Hold trigger to rear, bring hammer back and catch hammer via disconnect... slowly release trigger... did hammer trade off to trigger and stay, or did it drop?

If it dropped, remove the trigger and disconnect,  look at the disconnect spring anyway, as a few people have installed them backward and had similar problem.

See where the disconnect leg sits on the trigger, file the bottom of the disconnect leg so it will tip and grab the hammer shelf a bit deeper, don't need much though, re-test.

Ideally, the shelf on the hammer will pass the disconect hook so close so as not to hit, and not see any visible air gap (finger off trigger)

Very good SBR 7 11. Charles.