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2/16/2008 12:43:15 PM EDT
I'm new to AR type rifles so forgive me if the answer to this question is obvious.  I've got a Rock River Arms AR15 and I'm having problems with "doubling".  It only seems to happen when I go to really unload a clip.  I'll pull the trigger and get up to a 3 round burst instead of a single shot.  I'm told this could be caused by shots "cooking off" from the heat of the barrel or that it could be a problem of timing issues.  Any ideas or suggestions?? Thanks  
2/16/2008 2:00:37 PM EDT
[#1]
Cook offs take several seconds to occur.  If you are getting bursts, it is not a cook-off.

Most likely cause is a short, sticking or improperly installed disconnector, or a weak disconnector spring.  This is allowing the hammer to fall instead of being retained by the disconnector.  Things to try:
- disassemble the trigger, clean and oil all parts, reassemble making sure everything is going together the right way.  If that doesn't work...
- replace the disconnector spring.  If you still have problems...
- replace the disconnector

Report back how you made out.
2/16/2008 4:44:41 PM EDT
[#2]
www.ar15.com/content/guides/assembly/lower/

Above link to pull and reinstall the FCG if you have never done before.
notes,

When you push/drive out the hammer pin (retained by a J spring inside the hammer), hold the hammer in alignment (makes removing a installing the pin much easier).
The disconnector spring installs large coil side down into the back slot of the trigger.
The hammer spring legs will rest on top of the trigger pin.
The direction of the trigger pin is of no concern: either hammer spring leg will drop into the one side groove and retain the pin.
When installing the hammer pin, install the end without the annular grove inwards. This will allow the pin to slip into place, instead of having to drive the pins side groove past the J spring.
While you have the parts out, check the bottom of the lower receiver cavity for pieces of blown primers (love to hide in the grip hole threads).
As for cleaning and lubing the FCG parts (including the pins) CLP works the best.
3/1/2008 12:16:34 PM EDT
[#3]
.
3/2/2008 9:20:31 AM EDT
[#4]

Quoted:
Cook offs take several seconds to occur.  If you are getting bursts, it is not a cook-off.

Most likely cause is a short, sticking or improperly installed disconnector, or a weak disconnector spring.  This is allowing the hammer to fall instead of being retained by the disconnector.  Things to try:
- disassemble the trigger, clean and oil all parts, reassemble making sure everything is going together the right way.  If that doesn't work...
- replace the disconnector spring.  If you still have problems...
- replace the disconnector

Report back how you made out.


not to hijack the thread, i was having the same problems on a new m4 build..after reading this thread,found the disconnector spring was too short...just wanted to thank ya'll for the great info
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