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Posted: 9/26/2009 1:31:35 PM EDT
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Okay so i have an ar-15 that i inherited from my old man. I basically took the lower and put a brand new upper from m&a sales and went to the range. right off the bat it shoots one round and double feeds. once i clear the jam, i shoot again only to get a three round burst and then jams again. it basically rotates between a 1, 2, 3, shot burst with jamming after every burst. This apparently had happened before on the old upper. Its not the ammo because I've tried three differnt types already.
Need help or advice!!!! |
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Quoted:
Okay so i have an ar-15 that i inherited from my old man. I basically took the lower and put a brand new upper from m&a sales and went to the range. right off the bat it shoots one round and double feeds. once i clear the jam, i shoot again only to get a three round burst and then jams again. it basically rotates between a 1, 2, 3, shot burst with jamming after every burst. This apparently had happened before on the old upper. Its not the ammo because I've tried three differnt types already. Need help or advice!!!! You just admitted to owning a machine gun..Have fun in jail.... 
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Being the gun is malfunction, and not built into this, lets solve the problem of the defective weapon for it to fire correctly again (read not a machine gun, just a defective semi auto rifle in need of repair).
Start by going through link to understand the parts of the the Fire control group. The problem could be worn parts, or parts not installed correctly. http://www.ar15.com/content/guides/assembly/lower/ After going through such, you are going to pull the hammer, disco and hammer out of the lower, Here you want to make sure that there is nothing under the trigger in the lower cavity, and in fact that the disconnector spring is install, and it's large coil side down into the trigger slot. Once you have this down, and the rifle back together, I need you to hold the trigger back on the emtpy rifle, pull the charging handle all the way back, then let it go to slam the Bolt carrier home. After such, release the trigger and pull it again. We much first determine if the disco is retaining the hammer as the B/C slams home or not. If he hammer is retained on the disco during the B/C dry slam,Next I want you to do the same thing again, but this time as you release the trigger, so it very slow, then pull the trigger again. Here we are checking if the hammer is striking the firing pin at slow release, or if the hammer is just releasing to the trigger sear (read hammer should slip to the trigger sear, and on the pull after the release, then the hammer should be released to strike the firing pin. If the rifle fails either of the upper tests, then the next thing I need you to do is to shotgun the upper open, and with out touching the trigger, lower the hammer reward until you have gotten the back hammer sear as close to the disco sear as possible. The free gap between the two should in the .001" to .002" range. If greater than this, then the disc will need to be tuned correctly. To tune a disco, you will remove metal from the front bottom of the disco (where rests against the front top of the trigger) until the disco achieves this needed free gap stated above. Regarding the double feed and jams, this could be due to cleaning and lubing problems, short stroking, a bad mag, or a weak ejector spring dropping the case before the end of stroke. Here, we must first determine if the rifle is full stroking and the mag still in working condition. With double problems resolved, load only a single round into a mag, insert the mag and charge the round, followed by the singe round being fired down range. The end result needs to be that the bolt has locked back on the bolt catch via the follower tension of the empty mag and the rifle have full stroked. If the bolt did not lock back, then we will need to go into this further, but for now lets say it locks back, but the spent round only dribbled out of the ejection port (spent case went less than 10' when ejected). Here, you will go to a hardware store and pick up a #60 O-ring and install it around the outside of the extractor spring. This will increase the tension of the extractor spring to insure that the spent case is not dropped before the bolt reaches end of stoke. Also, before you reinstall the bolt back in the carrier after adding the spring, take a spent case and using the extractor, confirm that the ejector is moving in and out of the bolt face without binding (just spring tension). http://www.ar15.com/content/guides/parts/bolt.html Lastly, regarding the rifle, there are correct ways to clean and lube such, and incorrect ways. If the rifle is short stroking, first confirm that you are cleaning and lubing the rifle correctly, with the correct fluids (read Hoppes copper solvent chased with Hoppes gun oil are not the correct way for this platform). To get a better idea of how to clean and lube the rifle, here is primer for such, http://www.ar15.com/forums/topic.html?b=3&f=7&t=203988 P.S. Welcome to the site!!!!!!!! |
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