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Posted: 3/9/2012 7:18:36 PM EDT
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Hi all, I just built an AR from the ground up, and it cant fire more than one shot. I shot some wolf off to test it first, and it would not eject the round. So I emptied the mag except for one round of wolf and chambered it. It fired, but did not eject the round, the dead round kind of got jammed when the bolt started going forward without ejecting it. I thought it might be the bullets so i tried it a few more times with wolf and M855. 4 out of 5 times for both the wolf and the M855, the dead rounds would not eject. The other 1/5 of the time, the bullets ejected, but barely. The bolt would not catch open.
These are brand new parts, so before I went any further, I stuck the bolt carrier group into my other ar-15, and used the same mag. It shot it off perfectly. For kicks and giggles I stuck a different bolt carrier group into the upper that would not eject properly. I did not eject properly once again. Also I checked the lower on another upper and it worked. When installing the gas tube roll pin, it locked in the gas tube, but did not go through all the way. It broke a snap-on punch. I do not have another. It is in there snugly though, and will not move. The hole in the gas tube is line up with the gas block hole. I blocked this hole and blew into the gas tube, no air leaks. I monkeyed around a little bit, and moved the gas block around where the holes lined up and tried again, same results. My father and brother are of the belief the gas tube is not long enough. What is happening to cause this? It is an RGUNS Upper, RGUNS charging handle and M16 Bolt carrier group. It has a dez arms 18" rifle length fluted barrel, the roll pin and tube are both dezarms as well. The gas block is a combat optical tri rail gas block, it has 4 picitanny rails on it. Sorry for the spelling and thanks for any help! |
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Quoted:
When installing the gas tube roll pin, it locked in the gas tube, but did not go through all the way. It broke a snap-on punch. ummm.... sure you didn't squash the gas tube or something. breaking a punch is significant force on such relatively delicate material |
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What product did you use to clean and lube the upper bearings area of the new upper, and did you also you a chamber brush by hand before the new rifles madden voyage?
New/ tight/rough surfaces on the upper if correctly lubed, steel case ammo may be a problem until break in. Lastly, since you did have to work with gas tube, are you sure that the end of the gas tube at the receiver is correctly aligned with the carrier key, and even the FSB/gas block correctly aligned with the barrel gas port? |
I used ether to clean the surfaces where the extension and the receiver met and touch, then cleaned it with a rag. They both fit together nice, then I used wheel bearing grease. For the BCG and insides of the upper I think I used rem oil to clean, and then some gun slick to lube it up. Shes nice and slippery now! 
I figured out what the problem is though. The gas block is out of spec. The roll pin holes are too small, and they are set to far forward, so when the gas tube is pinned in, the gas port hole on the gas tube is partially covered.  Have to wait for another one to come now....
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Quoted:
I used ether to clean the surfaces where the extension and the receiver met and touch, then cleaned it with a rag. They both fit together nice, then I used wheel bearing grease. For the BCG and insides of the upper I think I used rem oil to clean, and then some gun slick to lube it up. Shes nice and slippery now!
I figured out what the problem is though. The gas block is out of spec. The roll pin holes are too small, and they are set to far forward, so when the gas tube is pinned in, the gas port hole on the gas tube is partially covered. Have to wait for another one to come now....normal for the roll pin hole to be smaller than the pin, If you use a pin punch tool, then the roll pin will not snap in half. Ditto on the passage to gas tube entry hole, and if you remove the back set screw on the block, can go straight up through the back thread channel with a drill bit to enlarge the gas tube end passage hole to match the gas block passage channel for it. As for matching the block passage channel to the barrel port channel, make a pencil line on the barrel shoulder TDC of the gas port, then use the tube as your guide to set the block correctly. From there, using your carrier without bolt, double check the alignment of the carrier key to gas tube, and if needed, tweak the gas tube center of barrel to align the key to gas tube. Also, mic the barrel shoulder to gas port, then compare that to the shoulder of the block to the center of gas passage before installing the gas block. Some block are meant to be used with the front hand guard ring (will require a small gap between the barrel shoulder to block), while others are not (block tight to the barrel shoulder). Regarding cleaning/lube, CLP alone (no grease), and don't forget to clean the chamber with a chamber brush and CLP before shooting the rifle as well again. The rifle is sent out with a storage grease on it(and any shop debris that the grease will collect), and that needs to be cleaned before the rifle is fired. Regarding lubing the upper bearing surfaces, CLP on the heavy side inside and out on the B/C, put the B/C that wet into the upper, and empty cycle the action a few times to migrate the CLP off the B/C to the upper receiver bearing areas. Once you get a few hundred rounds down the barrel, then you can clean the barrel bore with something like Sweets, but the rest of the rifle still gets cleaned with CLP (including the chamber with a chamber brush by hand after the bore has been cleaned). |
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Quoted:
normal for the roll pin hole to be smaller than the pin, If you use a pin punch tool, then the roll pin will not snap in half. Ditto on the passage to gas tube entry hole, and if you remove the back set screw on the block, can go straight up through the back thread channel with a drill bit to enlarge the gas tube end passage hole to match the gas block passage channel for it. As for matching the block passage channel to the barrel port channel, make a pencil line on the barrel shoulder TDC of the gas port, then use the tube as your guide to set the block correctly. From there, using your carrier without bolt, double check the alignment of the carrier key to gas tube, and if needed, tweak the gas tube center of barrel to align the key to gas tube. Also, mic the barrel shoulder to gas port, then compare that to the shoulder of the block to the center of gas passage before installing the gas block. Some block are meant to be used with the front hand guard ring (will require a small gap between the barrel shoulder to block), while others are not (block tight to the barrel shoulder). Regarding cleaning/lube, CLP alone (no grease), and don't forget to clean the chamber with a chamber brush and CLP before shooting the rifle as well again. The rifle is sent out with a storage grease on it(and any shop debris that the grease will collect), and that needs to be cleaned before the rifle is fired. Regarding lubing the upper bearing surfaces, CLP on the heavy side inside and out on the B/C, put the B/C that wet into the upper, and empty cycle the action a few times to migrate the CLP off the B/C to the upper receiver bearing areas. Once you get a few hundred rounds down the barrel, then you can clean the barrel bore with something like Sweets, but the rest of the rifle still gets cleaned with CLP (including the chamber with a chamber brush by hand after the bore has been cleaned). It was a combat optical gas block. The punch broke, not the roll pin lol. There aint no fixing this gas block with any drilling lol, it is way out of spec. Thanks for the indo on lining up the gas block, Ill put that to good use for the new one. Also thanks for the info on cleaning, Ima clean her up nice with clp before the next firing. |
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Update:
I got a UTG gas block. The gas tube insert area was not drilled open enough or it was burry....Yes, Poop luck. So we drilled it with the closest bit possible, maybe a thousandth of an inch of difference. Installed the gas tube. The gas block/gas tube now leaked air majorly bad........Now fed up with gas tubes and not wanting to wait longer for another one, we permanently affixed the gas tube to the gas block using sleeve sealant. We applied two coatings to the top of the gas block where the gas tube goes in and let it seep in(wiggling the gas tube helped it seep in). We pinned the gas tube into the gas block before we applied the sleeve sealant and made sure the gas port on the block and the tube lined up. After the hour wait time for one coat to harden we applied another coat. Then we waited 24 hours for the sealant to dry. After about 24 hours of drying we used Dano's pencil method to put the gas block on the barrel/upper. Shot the gun using tulammo. The damn thing still short stroked, so we used M855, and it shot perfectly. I'm guessing the reason for is the gas port was not opened up after the barrel was cut down from 20" to 18". Thoughts? |
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