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AR-15 Firing Question

MinerJohn

Aluminum
Joined
Dec 30, 2007
Location
Wisconsin
A buddy of mine called me yesterday about a problem he's having with his AR. Bear in mind, he assembled his own lower and I have not had a chance to look at it. He's put about 50 rounds through it and intermittently he would pull the trigger and it would fire off two to three rounds as if it were an automatic. I haven;t run into this problem but it sounds like a disconnect spring is either wrong or broken. Anyone run into this?
 
Yes, the problem is either a damaged component like a spring, wrong size, or it could be the timing of the trigger/disconnector/hammer.

This arrangement is called an 'escapement', and the basic idea is that the disconnector delays the unlocking of the hammer until the trigger nose can rise enough to intercept the hammer shelf on trigger release.
 
Three or four years ago I had one AR I had modified for a police department that would fire two, three etc. on occasion . A new disconect fixed it .
 
There is a case on a man named David Olofson who is in jail because of a semi auto firing more than one round per pull, it was due to a malfunction.

Is the disconnector functioning correctly?

I've not personally had this problem but I did dianose a buddies AR one time turned out to be a disconnector. Get it fixed before your buddy becomes like Mr. Olofson.
 
After a thorough inspection and you still cannot find something it could be the owner. I know it sounds funny but I tried helping out a buddy at work who only really ever fired from a bench, it ended up being that his grip and trigger pull caused 2 or 3 rounds to go down range. It wouldn't happen to anyone else. So he was bump firing. Some try to do it on purpose.

http://www.youtube.com/watch?v=QMoIocLvPSA&feature=related
 
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Most likely a disconnector timing problem. You need to make sure it has good engagement at the hook. There's a spec for clearance somewhere, but I can't find it. You adjust it by filing the underside of the tab at the front of the disconnector.
 
Also , find out what lower he used if the disconnector seems fine. Superior Arms and C3 Defense both have a set screwunder the grip that pushes on the bottom of the trigger to limit engagement (cheap trigger job is the intent). If it's in too much, it can prevent full engagement and cause doubles.
 
There is a case on a man named David Olofson who is in jail because of a semi auto firing more than one round per pull, it was due to a malfunction.

Is the disconnector functioning correctly?

I've not personally had this problem but I did dianose a buddies AR one time turned out to be a disconnector. Get it fixed before your buddy becomes like Mr. Olofson.

If you aren't familiar with this case, you need to study up. AR malfunctions can land you in federal prison.
 
Easy to functional test for this. Pull bolt back and release, pull trigger, hammer falls. Keep trigger pulled and cycle bolt. Release trigger and pull again, hammer should fall. Do this repeatedly before live testing. Glad I did this on my first one, really surprised me the first time the hammer didn't fall when I pulled the trigger. It fell when the bolt closed! The manufacturing tolerances on the disconnector aren't necessarily a drop-in fit.
 
Found the procedure:

With the upper off the lower, pull the hammer all the way back with the trigger untouched, until you can get the hammer rear sear edge as close to the disco sear edge as possible. The free gap between the two should only be around .001 to .003 (thickness of a hair) with the trigger at rest.

If the gap is greater than this, you will need to remove metal from the front bottom of the disco, where it seats/maxes out forward against the front top of the trigger. If you go this way, go slowly removing metal front the front bottom of the disco and check your progress often, since even a little metal removed from the disco will raise the disco forward at rest to close the gap quickly.
 
If you aren't familiar with this case, you need to study up. AR malfunctions can land you in federal prison.

While your studying the case realize too what a moron the guy was, and read over and over again how his AR-15 had THREE setting on it, one setting was unmarked and he allegedly told the guy he loaned the gun to not use that position because the gun would jam.

Lesson is, do not use M16 parts in your ar-15's. Not one single fore control part. ATF has been very clear for quite a few years that they consider any m16 fire control part in an ar-15 to constitute an unregistered MG. These parts include the trigger, the hammer, the carrier, and the selector. Even being in possession of these parts if you do not have an m16 but DO have an ar-15 can be construed as constructive possession of an unregistered MG.

Many ar-15 internals are probably case hardened, I would swap in new internals before I went to grinding and stoning on the ones you have now.

Bill
 
Timing the disconnector is standard practice. I doubt it's case hardened, files pretty easy. You might have to swap quite a few disconnectors if the root cause is misalignment of the holes in the lower.
 








 
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