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Posted: 3/29/2012 7:59:45 AM EDT
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I'm currently attending school that offers an awesome armorers and gunsmith program, and the instructor thought this would be a challenge for me and he's right. The only information i know about the issue is that it occurred over night. (the instructor said that the weapon fired and functioned fine the last few times out. and now this is happening)
Safe and Semi test and function fine, but the full auto test fails when the hammer does not follow the BCG back (forward). I appears to me that the BCG is not tripping the auto sear. the trigger will release the hammer once, but upon holding the trigger down, and charging the weapon once or repeatedly, the trigger will not reset. when opening the receiver, the hammer is held down by the auto sear. after opening the receiver, i can manually trip the auto sear and release the hammer to reset the trigger, or switch it back to semi witch moves the auto sear vertical and allows the trigger to reset, thus allowing me to pull the trigger with the receiver open (i cannot do this with the rifle closed). In class I began by cleaning the chamber and lug recess area and BCG to make sure there were no obstructions inside or out, the BCG rides forward completely. I also notices that the receiver halves cannot be closed while the weapon is in the full auto position, this leads me to believe that the BCG is engaging the auto sear, i can also hear the sear slap back if i open the rifle without having it charged and the selector in auto position. What am I missing? This is my first encounter with a full auto M16 (this rifle is not burst, i double checked) . One note, I did make sure it had an m16 BCG in the rifle (I was hoping he was trying to trick me!) Did I mention that after I get this rifle to pass its function test, I get to take it out to the school range and have my first full auto experience! |
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Either the auto sear or the bolt carrier has been altered or damaged.
You say you checked that an M16 BC was installed? Did you verify that the bottom ledge of the carrier is at the same location as the top ledge? Some "partial M16" bolt carriers are out there from years past, to provide most of the mass of the M16 carrier, without actually being able to trip an auto sear. If the carrier is fine, the top or back of the auto sear has been ground, peened or cracked off, such that the carrier ledge doesn't push it forward enough to clear the tang on the hammer. |
| while in class yesterday, I looked closely at the auto sear, it looked great, no rounded edges. also looked at the selector switch and sear spring alignment. all looked good. the hammer was in great shape too. the BC appeared normal m16 (1.5 inch rear or close to it, i didn't measure) and the gap in the upper to lower receiver was just over 1/8 inch (could be more but i was eyeing it) with the rear take down pin out and the selector in auto. (i used this simple idea to see it the sear was reaching the BC. I leave for class in about an hour, and I appreciate your help tremendously. I can take measurements but photos are outta the question. |
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Would help to know the FCG in the rifle, hence if a A-1 or A-2 burst trigger group.
If A-2, then double check the burst cam on the side of the hammer to confirm that the cam in not wedged/bound up or the spring broken, with the cam deep detent stuck so the secondary disconnector is retaining the hammer as you pull the trigger no matter what. [img]http://image.become.com/imageserver/s6/774445276-150-150-5-32/m16/m4-fullauto-and-burst-parts-cam-burst.jpg[img] If an A-1, then confirm that the selector is cam'g the disconnector out of play when set to full, hence the back tail of the disco now bent or broken, with the disco retaining the hammer when the trigger is pulled, the rifle charge and hammer not coming down as the auto sear is tripped. |
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