Hello all, I have a pre-ban Eagle Arms AR-15, using Colt magazines, and Federal surplus and Federal Green tip ammo. The last couple of times I went to the range, after a few clips, I would pull the trigger, and it would fire 3 or so shots one after the other. Then a couple shots later, it would fail to extract, and jam another round between the bolt and the chamber. I disassembled it, and everything seems to be in proper order. What could cause this? I was thinking the extractor could be bad, but why would that cause triple fires? Any help is greatly appreciated.
You pretty much firgured out the problem with the rifle running away.
If the disco sear is still in good shape, then maybe a new disco spring or retiming the disco will solve the problem.
As for the jams, could have been that the safety feature of the L hammer may have been kicking in, or the extractor or extractor was fouled out, or givein up the ghost.
With the rifle being a Pre ban unit, it may just need a few new springs to bring everything back up to speed.
What do you mean I figured it out, the extractor is bad? I was thinking about replacing the springs and stuff, but I would really like to figure out the actual problem before I just go needlessly replacing things. And I assume you mean the springs in the trigger assembly?
Lets take it from the top,
Pull the FCG out of the rifle, and once the parts are in hand and cleaned, check the sear on both the disconnector, and the back of the hammer (the sear that engages the disco). If this sears surfaces are still clean and sharp (read no chips or broken off points), then for the most part, the disconnector is savable. Also, check the disco spring to make sure that the large coil side is downward into the trigger slot, ad the spring is still in good shape. http://www.ar15.com/content/guides/assembly/lower/
Now with FCG clean/lubed and back in the rifle, we need to check the distance of the disco sear to the hammer sear with the trigger at rest. To do this, you slowly lower the hammer until the two secondary sears are at their closest point together. Ideally, the gap between the two sears should be around .003, but do to some wearing; the gap may be greater than that. If you find that gap is greater than say around .005, it’s time to retune the disco.
The disconnector is retained in the trigger via the trigger pin, and camed forward via the rear disco spring, with the front of the disco limited in it’s total foreword position via the contact it makes to the front of the trigger (bottom of the disco front onto the top of the trigger front top. When you retime a disconnector, you remove metal from the front/bottom of the disco to allow the sear of the disco to cam more forward. This allows the disco to have greater retention of the hammer when in play, and allows the disco to retain the hammer longer during trigger release for hammer reset. Ideally, a disco-grinding jig makes fast work of this (retains the disco contact angle to the trigger contact area, but if you are only dealing with retiming a disco for around .005, free hand shaving can be done).
Now this a math formula to figure out the amount to remove from the front bottom of the disco in regards to closing the distance between the sears, but again, since you will be hand shaving the disco (read using either a lapping plate or 200 wet/dry sandpaper on a flat surface and drawing the disco surface across to remove the contact area metal), you will need to do a couple of assembled test fittings to get the gap in the desired .003 range. Work slowly on removing amounts of metal, and watch the angle of contact of the disco/trigger so you do not change the disco angle (read have the hammer and pin handy to combine the three and insure that you are maintaining the same angle as you remove the disco’s front contact point to the trigger). Also, the reason that you will need to use sandpaper is that the disco is heat treated, and a file will do nothing. As for correcting with a jig (read angle control device that allows metal to be shaved using a fine wet stone grinder), the total process take less than a few minutes, including test fitting the parts to confirm that the disco is correctly timed.
Now the next item, the spent case Jamming problem.
As stated in the first post, the hammer has a safety feature called the L cut. What this boils down to is if the disco does not retain the hammer, the hammer will catch on the firing pin and prevent the bolt from closing. Once you have corrected the disco timing/engagement, this should prevent the runaway burst, and should resolve the jams as well. But, if the rifle continues to have problems with the extractor slipping off/past the rim of the spent round (read leaving the spent case still in the chamber), and you have maintained the rifle correctly (read correctly cleaned and lube), then additional tension to the spring, or the extractor corrected if worn. Since I don’t want write a novel (like I have start to do) and this rifle/parts are not brand new, lets just do a greatest hits on the parts and maintaining the rifle.
1. The rifle should be cleaned and lubed with CLP. If you have no idea what CLP is, just go buy a big spray can of BreakfreeCLP, and clean/lube the rifle per this, http://www.ar15.com/content/guides/maintenance/
2. The extractor spring should be strong and in good condition. When in doubt, replace it. If you have a fresh spring, and still having problems, you can add a # 60 plumbing O ring around the outside of the spring to add even more tension to the extractor, but the O ring is more of a band aid in regards to allowing the chamber self polish out threw live fire to break the chamber in. Again, since this rifle has a self polish barrel threw its live firings, is correctly cleaned, the O ring should not be needed (read chamber is smooth/clean/bur free, and the extractor is still in good condition.
3. The extractor its self should be in good working condition. To check this, pull the extractor off the bolt, and check the both the grabbing claw surface of it to confirm that it is sharp/bur free (read edges have not worn round nor milling burs present), and the case rim relief channel cut is burr free at the end (read the case rim can fully seat in the channel without end burs of the channel preventing seating). If you find production burs, remove them with a stone. If the extractor claw has worn out, (read edge no longer sharp), then just simple replace the extractor (again, check/correct the new extractor for burs before installing it.
To sum up the jam problem, the extractor/spring, may be the problem due to the age of the rifle, but most often, it is the chamber conditions and lack of proper cleaning technique that is to blame. Simple stated, I have correct more range jamming problems on other people AR with nothing more than a can of BreakfreeCLP, then having to correct/replace parts. Also, since I see that you are new to the site, my guess would be also new to repair on the rifles. Best bet if this all seems way past your skills is to just post over in your Home town forum (it’s one of the forums on the site) to see if there is someone that lives close to you, and check the rifle out and give you a hand if repairs are needed.
Hope this helps.