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Posted: 12/27/2012 4:15:58 AM EDT
I have a new R-15 that has had a few boxes of rounds run through it without issue during warm weather. This past weekend on a coyote hunt in 5 degree temps it would not hit the primer hard enough to fire rounds. It worked fine after a ride in the warm pickup so I am thinking it is a factory grease/oil issue. My question is where is the issue? Is the issue more likely in the bolt assembly or the trigger assembly? I did tear down the bolt and removed all the factory oil then lightly oiled the parts and reassembled. I did not do anything to the lower.
Link Posted: 12/27/2012 4:36:00 AM EDT
Link Posted: 12/27/2012 4:40:43 AM EDT
Thanks. Just to note I did not grease anything and would not grease anything. I meant whatever was in it from the factory. I did not find any grease in the upper but I didn't check out the lower. One question since I am a noob to the AR, what is FCG?
Link Posted: 12/27/2012 4:44:51 AM EDT
[Last Edit: 12/27/2012 4:45:02 AM EDT by AJE]
FCG = Fire Control Group, meaning the small parts in the receiver (trigger, hammer, etc)
Link Posted: 12/27/2012 4:49:57 AM EDT
Got it. Thanks guys. I will get some CLP asap.
Link Posted: 12/27/2012 4:58:54 AM EDT
Being from Minnesota i can say all it takes is a tiny bit of grease or thick oil on the firing pin and your out of action up here in the winter.
Link Posted: 12/27/2012 5:12:46 AM EDT
Link Posted: 12/27/2012 5:55:43 AM EDT
Yeah I live about 20 miles from the Minnesota border just into South Dakota so I know all about the Minnesota cold. I figured that no matter what lube I use I will go pretty light with it during the winter months. Thanks for the suggestions. Any idea what is the most likely culprit, bolt or hammer?
Link Posted: 12/27/2012 6:59:36 AM EDT
Link Posted: 12/27/2012 9:32:08 AM EDT
I will do some checking. The bolt seemed to shut as fast and hard as normal, but the sound of the hammer dropping on a dry fire was slow and soft. I am thinking you are right with the hammer on the hammer pin.
Link Posted: 12/27/2012 10:26:31 AM EDT
Link Posted: 12/28/2012 4:32:22 PM EDT

I'm going to go out on a limb here...

The OP says the rifle is fairly new, and refers to "factory Grease". I take from that he did not clean it thoroughly when he purchased it.

So my guess is that the firing pin had too much or the wrong type of lube for the cold shooting conditions. A slugish firing pin would cause light strikes.

Clean it thoroughly and lightly lube the firing pin, and the entire rifle, with something suitable for cold weather.

Link Posted: 12/28/2012 9:56:28 PM EDT
Link Posted: 12/28/2012 10:13:39 PM EDT
[Last Edit: 12/28/2012 10:14:34 PM EDT by Gamma762]
It likely did not have "lube" in it from the factory, most factory rifles have a thick preservative on the parts which should be removed and replaced with a proper lubricant.

For extreme cold use I would suggest one of the four lubes recommended from the (many years ago) RCMP testing. IIRC they tested at -40.

Which are:

Previously mentioned firing pin sluggishness is likely the cause of your problems.
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