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Posted: 3/30/2013 4:49:51 PM EDT
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Hey Guys,
So I got bored and rebarreled my stag upper with an AR stoner 1-7 twist free float troy rails and a gas block. Took it to the range with some new primary arms glass and shot it to find that it was a bolt gun. All I can think of is the gas block is not on straight. I pulled the rails and noticed that it was a little off, but no matter how turn it i can't get air to pass through. Any ideas? How do i make sure i have it right before I pound that gas block off of there again. Thank you, David. |
| Try pinning the gas tube to the gas block before sliding the block over the gas port. This way the gas tube if it is true when layed on a flat surface, it should line the gas block up with the gas port; as the gas tube slides into the upper receiver. This is the idea I have to lining it up. And, making sure the gas block is slid back far as it can go to where it meets up with the ridge on the barrel right after the gas port opening. |
| Which block? Some are made to accept a handguard cap, others not. If it "needs" a handguard cap and you skip it, the block's port will be behind the barrel's port. If it doesn't accept a cap and you used one, the block will be too far forward... I'm thinking yours needs a cap, and it is installed too far back, so the barrel and block ports just can't line up - this would make your attempts to rotate the block futile, because it isn't a rotation issue. |
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take a micrometer and measure the distance from the hole to the end on the gas block,
then do the same on the barrel then you can see how far forward or backwards you need to be, you could also make a mark on the barrel with a pencil so you know where to have the block +1 on putting the tube in the block first then putting gas block on barrel also, make sure gas hole in your swapped barrel isnt gunked up |
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Quoted:
Which block? Some are made to accept a handguard cap, others not. If it "needs" a handguard cap and you skip it, the block's port will be behind the barrel's port. If it doesn't accept a cap and you used one, the block will be too far forward... I'm thinking yours needs a cap, and it is installed too far back, so the barrel and block ports just can't line up - this would make your attempts to rotate the block futile, because it isn't a rotation issue. Probably relates to this.... In the mean time grab a piece of plastic tubing and place it over the gas tube where it enters the upper receiver. Blow some air through it to see if it's clear, if your a smoker you'll see the tell-tale signs..... or not. |
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there's a washer (shim) made that's the thickness of the handguard cap that's used with free floats.
alternatively, you can make the hole in the gas block (NOT THE BARREL!) larger. it's larger than the gas port anyway, so it just makes it (the block) a little more forgiving. and you shouldn't have to "beat" anything off ,(no smutty joke intended). if tapping it with a screwdriver handle or such won't do it, fix the problem. |
| Although it may seem odd, get some compressed air or air from an air compressor, or put your mouth on the barrel end, plug your finger in the breech and blow air until it's coming out the gas tube. Then mark it and you'll know. Takes just a few seconds and you don't have to guess or worry that it won't work. You just heard the air, the gas will flow the same. |
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Well this is awkward... I had the gas tube in upside down. Yeah... So who should I turn my gun guy card in to. Ha!!! Shit happens. We all make mistakes. Most people arent man enough to admit it on the interwebs, props to you. Flip it, put it back the right way and go to town. I know on AR10s, you have to account for the small gap that the hand guard end cap makes. Armalite uses shims in place of the end cap to be used for free floats hand guards. Im not sure if this is the case with AR15s. Mine have all been basic builds, nothing fancy. So they all have the standard handguards and end caps. |
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you probably have it pushed all the way back against the front site shoulder on the barrel and the gas port may be further forward. You can use feeler gauges to piddle with the gap. Yep. Easiest way is to use shim stock washers to push it out far enough to simulate the existence of a handguard cap. ETA yikes I didn't know you could put in a gas tube upside down. |
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Well this is awkward... I had the gas tube in upside down. Yeah... So who should I turn my gun guy card in to. Been there done that 
I was actually gonna suggest checking this, until I saw you fixed it. I didn't think it was possible to get the gas tube through the receiver upside down, but obviously you can. Glad you got it fixed. |
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