So a while ago my cav arms ar15 began shooting random bursts of 2-3 rounds but it was too random an occurrence that some days it wouldn't happen at all.  Lately it's been doing it almost every trip.  I thought mabey my cleaning methods weren't up to snuff  so I had my local gun shop do a head to toe cleaning.  Took it out for a spin and it kept doing it.  What in great google moogle could be happening to cause my gun to burst like that and how can I fix it?

Thanks in advance.

Most likely your disconnector REPLACE IMMEDIATELY!  ATf have come down on folks in the past for that very reason.

you mean like the Guard guy from wisconsin

Definitely something amiss in the fire control group, probably a disconnector as mentioned earlier. Get it fixed ASAP.

Don't screw around and shoot it again, you can get into serious trouble.  BATF&E can confiscate ever fire arm you own and convict you of a felony with possible jail time.  All for a $5 part.  II you know how to work on the FCG replace the disco, if not, replace the entire FCG.

Could be your disconnect, trigger, or hammer. To diagnose:
Remove your lower and cock the hammer. Pull and hold the trigger to the rear while riding the hammer forward, then cock the hammer again while still holding the trigger all the way to the rear. The hammer should engage the disconnect and stay to the rear. You should be able to do this thousands of times without the hammer falling forward. If the hammer falls while you're holding the trigger to the rear, replace your disconnect. If the hammer falls when you release the trigger, either your hammer or your trigger is installed wrong or you need to replace one or both.
Hope this helps!

agree with respect- function check the disconnector as described. if faulty replace if you can't reporduce with a function check take it to a smith. i have also seen a spent primer get in the fire controls and cause this.

I appreciate all the help.  You guys are awesome!  I went out and got a dpms lower parts kit to fix this whole mess.  I had no idea that something like this could have such serious ramifications.  Anyways, thank you all and I'll follow up after performing all of the above.

For the new guys, this is old hat for the "old timers". In my experience, using one of my lowers, a missing or collapsed disconnector spring will cause full auto fire. If you keep the trigger pulled with a connector missing or a connector spring missing, the BCG will continue to cycle. An upside down spring stuck down will do the same. As long as the trigger is pulled, just like a M-16, the rifle will continue to cycle. Once the the trigger is released the trigger catches the hammer and the rifle stops cycling. With the spring missing or sticking, bursts may be intermitten if the disconnector happens to flop forward during the process and catch the hammer.

I did not try this with live fire, merely testing the mechanics of the FCG. It consituted a function test with the disconnector missing and then with the disconnector spring missing. The function test failed in both conditions.

So I performed all of the function checks before working with Tyne new trigger assembly.  Everything was working fine.  At that point I took it to a gun smith at my gun club and he said my hammer was a little old school and larger than most.  It was striking the disconector in such a way that it wouldn't always catch which is why the problem was intermittent.  Im actually putting the parts kit aside for a bit, ordered a spikes battle trigger and installed it.  I'm taking it to the range tomorrow.

I guess that's why I avoid "trick" triggers. The Spikes battle trigger is a wise choice.

is there anything else that can cause a double fire other than the secondary disconnector?

Faulty disconnector, disconnector spring, disconnector pin, hammer or trigger could cause a double.  Most often caused by the disco and/or disco spring.  Keep a spare disco and spring on hand, they're cheap.

Missing, damaged or improperly installed disconnector spring, improperly timed disconnector, damaged disconnector or hammer, improperly installed hammer spring or wrong pin size FCG installed.



 

The new trigger/hammer did the job.  It's harsher/crisper than I'm used to but I'm sure that a good little break in period will do the job.  Damn, looks like I have to go to th range again tomorrow

A dab of good grease on the contact surfaces helps and dry fire the heck out of it.

I usually polish out the contact surfaces but wear will do it for you also......I usually cycle the AK,s about 200 times before I test fire them.... It work also on the AR,s its just alittle harder.......