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Posted: 12/17/2007 9:25:25 AM EDT
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I am experiencing an occasional undemanded "double tap," two shots firing like a short full auto burst. I am using a Ceiner kit in a Bremmer lower, Accuracy Speaks dedicated upper and trigger and Black Dog mags. I have cleaned and teflon lubed everything, and as it seemed to be sticky and not very free moving removed the firing pin from the bolt and cleaned a lot of crud from the hole. The firing pin is now freely moving but I am still getting the two shot burst, not very often but it could be a problem in some competitions. It is not ammunition related, it can happen with any of the 4 or 5 types I have been using. I have checked the operation of the trigger disconnector by holding back the trigger, cocking the hammer and letting go the trigger. The hammer holds correctly every time and is good and crisp in it's action. One suggestion has been that the firing pin spring is weak and I am suffering slam fires: any views on this, and any ideas how to fix it?  |
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Sounds like your bolt is not coming back far enough to recock the hammer. I went with the Lakeside Machine springs and my doubles went away  the recoil spring did the job http://www.jbarms.citymax.com/catalog/item/3766994/3541941.htm It now will cycle all sub ammo i feed it after the spring swap. . |
| I've experienced this numerous times when shooting low powered 22LR ammo. It appears there is not enough energy to cock the hammer (to catch and hold against the sear)and the hammer rides down with the bolt hitting the firing pin causing the next round to fire. I've experienced this on every AR conversion kit I've used. The only other times I have had this happen was with 5.56's where there was a defective hammer/trigger combo. I personally don't like it when this happens. Its very unnerving when this happens with 5.56 and isn't supposed to. It doesn't bother me to fire full auto I just like to be able to know when it is going to happen. On one a occasion a RRA NM trigger got very light and started doubling after only a few rounds. RRA was contacted and rectified the problem no questions asked. Can't say for sure if this is what is going on with your weapon but I definitely would try some good High velocity 40 grain ammo. If it still continues I'd get the trigger group inspected by an armorer/gunsmith! |
I have tried a number of standard and high velocity ammunition types, it does not appear ammunition related because it occurs with any. If anything it seems more frequent with HV ammunition, I fired a couple of magazines of CCI Mini Mags at the weekend and it happened several times. I don't mind full auto but it is illegal in the UK and can be a problem in a competion where a single shot is required! 
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You may have a point, the nut behind the trigger can cause all manner of problems if not adjusted correctly! Thanks for the advice, I have been aware that this could be the problem and have tried to be alert to anything unusual when firing but have not yet been able to detect an impending double. I have taken the advice of Kevin at Black Dog Machine Tool and shortened the recoil spring 1". Update after next weekend's range outing. Martin |
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