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Posted: 8/27/2010 2:25:27 PM EDT
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Newbie trying to help another newbie here, so please be gentle...
I met my friend at the range today to shoot our AR's. His is a used rifle that he bought from a local gun shop. He had not fired it before today. On his first shot with a full mag he got a double fire - 2 shots! The second round didn't eject cleanly and was jammed with the third round. We took the mag out and cleared the jam and did all we knew to do, which was basically to work the bolt a few times and then put the mag back in. Second attempt to fire resulted in the same thing - double fire with the second empty and third live round jammed. We tried different ammo, different mags and all had the same results. With the gun empty and no mag, we were able to isolate this: The trigger is pulled and held and there is a click of the hammer falling. With the trigger still held the bolt is pulled back (as if to eject a round) and then locked forward. When the trigger is released, it sounds like the hammer falls again. It seemed to us that this was what was causing the double fire but we couldn't figure out why it was behaving this way. My gun doesn't do this. We continued to shoot his gun single-shot and while all of them fired and the bolt locked back, he had several rounds that didn't eject properly. The were free from the bolt face but were just sitting in the open eject port. The rounds that did eject were ejected to the front, I'd guess around 1-2 o'clock. My friend took the gun to the shop where he bought it and he said they replaced the entire trigger mechanism and the extractor. I'm not sure if this included the hammer, sear, etc. He hasn't fired the gun yet but said that about 1-2 times in 4 the gun still does the same thing when dry firing. He wants to meet at the range and shoot again but it sounds to me like the problem isn't fixed. Sorry for the long post but wondering if any of you have ever seen anything like this or might know what the problem is. TIA, Mike ETA: Realize now this probably be in Troubleshooting forum. Sorry. |
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Could be a lot of things.
No disconnector spring Disconnector spring installed incorrectly No disconnector Worn are altered trigger or hammer engagment surfaces. Worn disconnector Out of spec lower Improperly adjusted adjustable type fire control group. Broken hammer pin |
| I had the same problem on my dedicated 22, I took the fcg out and noticed I had installed the disconnector spring upside down. I haven't been able to do a live fire test yet, but it passes the function test and the disconnector moves alot easier than it did when the spring was in wrong. |
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I am a Marine armorer. A double fire is normally caused by worn disconnector or hammer, (or burst disc or disconnector but this doesnt apply to you!)
Normal funciton check is as follows charge the rifle place on fire pull and hold the trigger - you should hear a single click (this is the hammer striking the firing pin) charge it again while holding the trigger slowly release the trigger - you should hear a clunk. (this is the disconnector releasing the hammer) ( the gun should not fire!) pull the trigger again - you should hear a click (if you didnt hear the click open the gun and see if the hammer is forward. if the hammer is forward then the disconnector released the hammer early and the trigger did not catch the hammer like it should) this works. This is not a great explanation. If you want to see it in detail look it up in a military 23&P tech manual. ETA: Here is the WP as it deals with semi ALL WEAPONS 7. Make a functional check on an assembled weapon with selector lever in SAFE, SEMI, and BURST/AUTO positions. Any portion of this check may be used alone to determine the operational condition of any specific firing position selected. a. Remove magazine if installed. Pull charging handle assembly to rear. Check that chamber is clear. Let bolt and bolt carrier assembly close. Do not pull trigger. Leave hammer in cocked position. WARNING If weapon fails any function tests, perform required maintenance. Continued use of the weapon could result in injury to, or death of, personnel. b. Place selector lever in SAFE position and pull trigger. Hammer should not fall. c. Place selector lever in SEMI position. Pull trigger. Hammer should fall. NOTE For the purpose of the following check "SLOW" is defined as 1/4 to 1/2 the normal rate of trigger release. d. Hold trigger to the rear, charge weapon, and release the trigger with a slow, smooth motion, without hesitations or stops, until the trigger is fully forward; an audible click should be heard. Hammer should not fall. e. Repeat the SEMI position test five times. The weapon must not malfunction during any of these five tests. If the weapon malfunctions during any of these five tests, repair (see WP 0021). |
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