OP
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Hammer is not following the bolt down now. Trigger is standard weight. It's a brand new, unaltered lpk used for the very first time.
AR Build Problem
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Forgive me if I missed it after reading through the thread twice, but what lower are you using?
[fighting the flu and concentration is not what it should be]
Doesn't take much misalignment on the trigger pin to "torque" the parts enough to make them bind. Other than pin axis, could be a defective part; trigger or disconnector hole drilled off-axis or with a burr. Just as an experiment, try polishing both sides of the disconnecter with 600-grit on a really flat surface and re-installing with a new spring.
As already mentioned, the disconnector spring must be installed larger-diameter coil down into the trigger. Otherwise it likes to wallow around and shift off perpendicular.
Lastly, and not to insult your intelligence, what lube are you using and where are you putting it in the trigger group? I've become a big fan of the super-synthetics...they work well, last longer and can make a real difference in trigger pull-weight.
Good luck...
[fighting the flu and concentration is not what it should be]
Doesn't take much misalignment on the trigger pin to "torque" the parts enough to make them bind. Other than pin axis, could be a defective part; trigger or disconnector hole drilled off-axis or with a burr. Just as an experiment, try polishing both sides of the disconnecter with 600-grit on a really flat surface and re-installing with a new spring.
As already mentioned, the disconnector spring must be installed larger-diameter coil down into the trigger. Otherwise it likes to wallow around and shift off perpendicular.
Lastly, and not to insult your intelligence, what lube are you using and where are you putting it in the trigger group? I've become a big fan of the super-synthetics...they work well, last longer and can make a real difference in trigger pull-weight.
Good luck...
Redlg155
Member
I would definitely try a new fire control group to see if it works. Even of you got the bug worked out, could you really trust it after this with the old fcg?
OP
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I think I found the culprit, at least generally. The gun still has light primer strikes about 7 out of 10 rounds. I decided to pull the BCG from my rifle and try it with the SBR. With the different BCG, the SBR now runs perfectly!
It was too cold to try the SBR bolt in the rifle to see if just switch them will work for both guns.
It was too cold to try the SBR bolt in the rifle to see if just switch them will work for both guns.
jmorris
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If that doesn't work. Take the working BCG and swap the bolt in from the non working BCG to the "good" one and see if it runs.
If it does swap the firing pin, etc. Until you have all of the parts except the carrier swapped. At that point put all of the "good parts into the nonfunctional BCG and see if it works at that point.
You have already narrowed the search for the problem down to the BCG so you only have a few steps left.
You might even get lucky and find, due to tolerance stack, that both work with the right mix of parts.
If it does swap the firing pin, etc. Until you have all of the parts except the carrier swapped. At that point put all of the "good parts into the nonfunctional BCG and see if it works at that point.
You have already narrowed the search for the problem down to the BCG so you only have a few steps left.
You might even get lucky and find, due to tolerance stack, that both work with the right mix of parts.
jmorris
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Being clean has nothing to do with anything. A single part built out of spec, or assembled wrong, can cause the entire device to fail.
Remember the space shuttle that destroyed 7 lives and cost $1.5 billion in 1986, failed because of an o-ring.
Just because something is new or expensive does not make it perfect. There was also your hammer follow problem that fixed itself.
Lucky for you, your problem will be easy to find and cheap to fix, once you locate it and there are just a few parts that can be the problem, now that you have it narrowed down.
FWIW I would sooner put my trust in a rifle that had 10,000 rounds through it than any out of the box.
Remember the space shuttle that destroyed 7 lives and cost $1.5 billion in 1986, failed because of an o-ring.
Just because something is new or expensive does not make it perfect. There was also your hammer follow problem that fixed itself.
Lucky for you, your problem will be easy to find and cheap to fix, once you locate it and there are just a few parts that can be the problem, now that you have it narrowed down.
FWIW I would sooner put my trust in a rifle that had 10,000 rounds through it than any out of the box.
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Who made it?
When you disassembled and inspected/lubed it during installation did it all seem right?
OP
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I gave the bcg a more thorough inspection and compared with my other one that runs as normal. I think I found the culprit. The tip of the firing pin doesn't stick out of the bolt face enough. It's just barely enough to catch a fingernail on. Compared to the good bcg, it's firing pin sticks out of the bolt a lot farther.
Tried measuring lengths of firing pins, but the battery was dead on my caliper. By eyeball, the newer firing pin is a hair shorter than the older one.
I tried the longer firing pin in the newer bolt and it's still doesn't stick out as much as it did when it was in my good bcg. So I'm thinking its a two-part problem, a firing pin that's a hair too short and a bolt that's a hair too long.
Tried measuring lengths of firing pins, but the battery was dead on my caliper. By eyeball, the newer firing pin is a hair shorter than the older one.
I tried the longer firing pin in the newer bolt and it's still doesn't stick out as much as it did when it was in my good bcg. So I'm thinking its a two-part problem, a firing pin that's a hair too short and a bolt that's a hair too long.
I just had this problem with an AR I built over Christmas. The problem is with the disconnector where it engages the hammer. The angle, finish, and spring tensions are very critical here, and if not right, the trigger won't return when released after firing, or the hammer can follow the bolt forward if the disconnector slips.
My problems arose while working with the trigger pull and over-travel. In the process I ran into disconnector issues, and finally gave up and ordered a Rock River match trigger group for about $99 delivered to my door. It took about 5 minutes to install it, and I never have looked back. The pull is fantastic with no overtravel. Problem solved. Well worth the $99.
My problems arose while working with the trigger pull and over-travel. In the process I ran into disconnector issues, and finally gave up and ordered a Rock River match trigger group for about $99 delivered to my door. It took about 5 minutes to install it, and I never have looked back. The pull is fantastic with no overtravel. Problem solved. Well worth the $99.
You found your problem
OP
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Let's just calm down a little here. None of my ARs are defensive guns. They sit in the safe. Whether I can "trust" them is up to me. And frankly, that aspect is completely irrelevant here.
I'm simply trying to troubleshoot a malfunction. Anything other that is not something I care to discuss our debate.
I'm simply trying to troubleshoot a malfunction. Anything other that is not something I care to discuss our debate.
OK, I deleted a bunch of posts that were pulling us away from the problem stated by the OP. I will not let the obsessive nature of a couple members totally derail a valid thread from another member simply seeking help. Once the OP is sure he has identified the problem part or parts he may post who made them. If he chooses to do so. Until then, drop it.
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