Upon completing my new ar15 build I went to the range to do a test fire.  The first shot fired fine, upon trying to shoot the second shot I noticed the gun was not cocked, so I pulled the charging handle to chamber a round and cock it, a unfired shell with a half hit primer come out.  I figured it was just a bad shell so I chambered the next round from the mag.  When I shot this time, it shot the last 2 rounds in the clip in a double tap speed.  This scared the hell out of me and people were kinda looking at me at the range, of course the range officer had some questions for me when he heard it shoot like that.  Other than that it fires single rounds from the mag just fine.  But when there is more that one round in a mag (never tried more than 2 rounds in mag) it fires them very quickly.  Of course I would not mind an ar that is full auto, but I paid for a semi auto rifle that wont get me in trouble at the range.   If anyone knows what could cause this please help.

M4A2 Carbine with mil spec 16 inch barrel

disconector spring

Disconnector spring or bump fire.

Try this

MAKE SURE GUN IS UNLOADED!

cock rifle

pull trigger and continue to hold trigger to rear.

while holding trigger pull charging handle and cock rifle again.

if the hammer follows the carrier forward then you have a disconnector problem.

You guys are right, as soon as I read your posts I realized I put no spring in the dis-connector.  I had no left over parts in the bag, but upon inspecting the package the kit came in there was a little spring in the bottom corner of the box.  Thank you very much for the help!!

This is why you FUNCTION CHECK a firearm prior to shooting it.

You might mind the $10,000 fine and the 10 years in Federal pound you in the a## prison though.  Seriously don't shoot it any more until you fix it and get successful unloaded function checks.

DELETE THIS FUCKING THREAD NOW.

It makes my day anytime someone quotes that movie.   "Uhmm,  yeea, Im gona need you to come in on saturday"

And hide your dog!

My first post wasn't near this epic....

function check -

This.

You might go ahead & get rid of your full auto carrier & replace it w/ a semi carrier that leaves the back of the firing pin exposed.  What is happening is that the hammer is falling as the carrier goes into battery as long as you hold down on the trigger.  W/ the semi carrier, the hammer will get caught on the back of the firing pin & will catch the BCG and keep if from chambering & locking.

It is true that you cannot be conviceted for having a full auto carrier alone, regardless of what the bushmaster catalog says.  However, if some ATF lab tech can get your gun to even double on camera, or worse if the disconnector breaks etc, you could be made an example of.  That poor guardsman basically got sent to prison for something like this happening.  

Additionally, this is dangerous b/c the may be some slight possibility that the hammer could hit the pin & the primer before the gun is fully in battery.  This is why a real full auto has a full auto sear, to ensure that the hammer doesn't fall until the breech is fully in battery.  If the gun fires out of battery, you get a KABOOM which could cause injury to your face & eyes!  

Don't be an example for the ATF to use to try to establish that the AR is "readily convertible".