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Posted: 12/17/2010 5:21:28 PM EDT
I saw a friend who I have not seen in awhile. He told me he had decided to build a rifle with a Spikes lower, DD lower parts kit, BCM upper and BCG, and a RRA stock. He said his rifle is running fine with no jams and is very accurate. There was just one problem. He told me he is getting mutiple shots with one pull of the trigger from time to time. He said these burst range from a double tap to four shots. It freaked him out a little since he had used quality parts for his lower. He said on the two occasions he had fired it these burst did not happen until he was on his third mag of the day. He was about to order another LPK but I told him it sounded like his hammer or disconnect was the problem. He said his hammer is not notched. I told him to order another hammer and disconnect and to replace the disconnect first. If the problem goes away then he now has a spare hammer and vis versa if the hammer is the fix instead of the disconnect. Was this bad advice? I also told him to register here since the site is a wealth of info. Thanks for advice that I can pass on to him.
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| If the rifle has been doing the "burst" thing since new then I would say he has the disconnector spring in upside down (goes fat end down into the trigger body) or the disconnector/hammer is damaged or out of spec. If this is something it just started doing after functioning flawlessly for awhile then I would say a popped primer or some dirt/debris under the trigger body. When every I see these types of threads I always ask them to check the disconnector spring first ... hope that helps. |
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The problem is as stated, stemming from the disco not regaining the hammer correctly before the trigger is released to reset the hammer.
Confirm that the FCG is the correct pin size for the lower, then disco spring is the correct spring and installed large coils side down into the trigger slot, and the disco is in the correct timing as well. If the free gap between the hammer and disco with the trigger untouched is too great, then the disco will not correctly retain the hammer at trigger help back, and allows the hammer to be danced off the disco as the B/C come crashing home. On disco timing, with the trigger untouched, pull the hammer back until you have the rear hammer sear and the disco sear as close to each other as you can. The free gap between the two should be in the .001 to .003 range (about the size of a human hair) and if he finds the gap to be too large, then metal is removed from the front/bottom of the disco where it forward maxes out on front/top of the trigger. And here is the lower parts so he can figure out if he has the wrong spring installed for the disco. 
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| Thanks for the help guys. I have several spare disconnectors and multiple disco springs so I lent my friend a disconnector and spring. Problem solved. He ran five mags, about 100 rnds total with no issues this afternoon. I'm pretty sure it was the original spring from DD. We compared it to several of the replacement ones I have and it was noticeably shorter. |
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