new AR, and problems

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It wouldn't hurt. It routinely gets blown out with 50,000 psi. ;)

Any carbon streaks/soot etc. around the gasblock, gastube hole, or barrel?
 
not that I can TELL...I made the mistake of spraying Powder Blast as a blockage check and that stuff dries white, making it a little hard to tell. the tube was dirty around the holes where it enters the gasblock...i cleaned it though nothinking id need to take a pic...


Gastube is out. When I spray powder blast from the receiver end, it leaks out the gas block end. However, does the gas block end have a one way valve? The ends are definitely different...pics incoming soon...can't see any major defects in the tube, although there is a place towards the receiver end where it either tapers a bit or has a verrrrrry fine crack, I can't tell....
 
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OK, last part to check is the gas block. Shoot some Breakfree into the spot where the gas tube goes into the gas block, it should come out in the barrel. If it doesn't then, that is your problem.
 
when i squirt powder blast into the gas block, it backs up, rolls out the gas tube hole i sprayed it into and also comes out of the roll pin hole...doesnt really come out in other places....
 
The whole point of the gas block is to mate with a hole bored sideways into the barrel. Gas from behind the bullet travels through the hole into the gas block, down the tube, into the carrier, and opens the bolt.

The gas block moved and is blocking the hole in the barrel. This is not uncommon with blocks not set up correctly. Taper pin blocks are drilled through with pins tapped one way. Allen screw gas blocks are supposed to have dimples drilled into the barrel to prevent them moving.

Loosening the screws and moving the block will show if the dimples exist. IF they are there, put the block in the correct place, use red loctite on the screws and tighten.

If they aren't there, oh well. You have to measure the block and fit it to be directly over the hole, drill the dimples, and loctite the screws.

As for it coming loose, if this is the case, the assembler gets an F for Fail. Set screws are not milspec, another F for Fail. Putting the rifle together and selling it to you, another F for Fail.

Friends don't let friends buy guns that are less than milspec. Kinda like assembling an AK kit gun with pop rivets. At least this is repairable and actually a simple problem.
 
thanks Tirod. that actually makes a lot of sense. my barrel does have the hole and the dimples....


now getting this tube back is sticky...it isnt straight so theres parts where it gets stuck...should i just tap it through or whats the best way to reinsert and reposition the gas tube into the block?
 
here's where I'm at. As Tirov said, I'm pretty sure it was a misalignment of gastube and block with hole in barrel or combuination of the three. I've gotten removing the whole thing down, I removed, cleaned, lubed and checked for obstructions, blew out with compressor and reassembled using BLUE loctite (for now) on the set screws.


Going to test fire again this weekend. IF it does the same thing, I'm going to try and send it to JP Enterprises as it's a JP/Doublestar assembled gun. from parts. If they can't help me, it's gunsmith time. But thanks to you guys, I at least know enough now not to be gouged on it. Thanks again!!! keep chiming in with any pertinent info/hints. thanks!
 
Acceptableusername, look back at the photo you posted of your gas block at 8:01, first picture. Your problem is visible right there. Can you see the gap between the gas block and the handguard retainer? It shouldn't be there.

You need to loosen the two set screws that hold the gas block, and use a mallet to tap the gas block down until it holds the handguard retainer securely against the shoulder on the barrel. Then, tighten the set screws again. Your gas block is probably aluminum, so don't go nuts tightening them or you'll strip out the threads, but they do need to be snug.

If you want an extra measure of security, you can use a punch and hammer to stake the set screws in place so they can't back out. If you don't stake them in, you definitely need to use Loctite on them. Blue will be adequate.

The gas block set screws were probably not torqued correctly in the first place, and the guy who assembled it probably didn't use a thread locker either. Repetitive recoil or maybe a hard bump on the handguard in the right direction must have moved the gas block.


[Edit] Didn't read far enough down to see that you had got it figured out. Eh, I'll leave it up anyway.
 
this thread is treading on sticky territory I'd think....extremely valuable, to me at least. You guys are lifesavers.


Got everything on tonight snug, though my gas block looks a little crooked. But for all intents and purposes, I think I'm set. Will disassemble, clean and oil again and reassemble carefully tomorrow. Will shoot, and report back. Sunday night at latest.
 
This has been a fun exercise in troubleshooting, and is an excellent example of why pins are the best way of fastening a gas block. Set screws have their place, but pins are king. I'm glad your rifle is back in commission.
 
it isnt yet...but I'd bet before the weekend is over, it will be. thanks to all the advice in this thread. I'm not sure, but I may still have a bad extractor. I can't get it to budge under finger pressure at all. Maybe they're supposed to be just that stiff?

At any rate, I'm probably going to look at some small dollar upgrades, what would you guys recommend? I'll pick up a spare bolt assembly for it in the future and probably for every AR, but right now how can I upgrade for cheap? This means new gas tubes, extractor, any kind of buffer, etc?

Beyond getting this rifle dialed in, I'm not going to do much to it but put a sling and light on it and mount a cheap NC star holo sight (45 bucks, lifetime guarantee, day and night settings, red and green reticule, all steel, not bad for a budget AR?).
 
I'm not sure, but I may still have a bad extractor. I can't get it to budge under finger pressure at all. Maybe they're supposed to be just that stiff?
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They're meant to be pretty darned stiff. If you're worried about it, you can replace the spring kit with the unit from BravoCompanyUSA.com that I linked to earlier in the thread. It's a cheap thing to replace for a little piece of mind.

At any rate, I'm probably going to look at some small dollar upgrades, what would you guys recommend? I'll pick up a spare bolt assembly for it in the future and probably for every AR, but right now how can I upgrade for cheap? This means new gas tubes, extractor, any kind of buffer, etc?
Click to expand...
The extractor upgrade will get you a known-quality extractor spring kit. That's cheap peace of mind. I'd also stake or re-stake the carrier key and buffer tube end plate (assuming carbine stock) if they need it.
End plate staking: http://m4carbine.net/showthread.php?t=6994
Gas key staking: http://m4carbine.net/showthread.php?t=6993
I'm also going to assume your rifle has a carbine buffer and a semi-auto carrier. You may want to go up to an H buffer if you're getting overly-strong ejection (dents in the cases, or ejection between 5 and 6 o'clock).

Beyond getting this rifle dialed in, I'm not going to do much to it but put a sling and light on it and mount a cheap NC star holo sight (45 bucks, lifetime guarantee, day and night settings, red and green reticule, all steel, not bad for a budget AR?).
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If it were mine, I'd skip the optic for now and put that money towards ammo or saving for better glass. I'd rather have good irons than a low-budget optic anyway.
 
I'm probably going to look at some small dollar upgrades, what would you guys recommend?
Click to expand...

I'm not big on the add-ons, but the T-Pod might be a good one for you.
Probably, you'll need a rail-mount sling swivel to get a second sling attachement point. But, that will work for a one-point, as well.

Really, though, the best thing is a good case. Mine is a Waller and does not shout "EBR" while having plenty of storage for mags, cleaning kits, and the like.

If you can, find a nice bulk pack of gas tube pipecleaners. Also, there are some very nice chamber cleaning kits that help you help gas-operated ARs run.

Oh, for under $20, they make a cool tool to remove spring handguards (which you've already learned are far too mush fun <g>). AccuWedge not a bad thing to have, and cheap. The nifty Sampson grip insert/tool looks right cool, too (failed to get one at the Reliant Show last week, though--dumb).

Best thing to get for your AR is $3 box ammo, sadly, that's all $6 a box anymore (or was last week).

That's my quick 2¢
 
I'm not sure, but I may still have a bad extractor. I can't get it to budge under finger pressure at all. Maybe they're supposed to be just that stiff?
Click to expand...

It is stiff because of the black polymer O-ring around the extractor spring. This is an aftermarket addition meant to combat "Extractor lift". When the M4 cycles, the extractor briefly lifts off the rim of the case as it is going backwards, normally, pressure at this point is still high enough that the case is held on to the boltface by the pressure until the extractor claw settles back down; but sometimes not.

The O-ring fixes this and adds extra tension to the extractor to keep it from slipping off the case rim (since the carbine extracts under higher pressures than the rifle).

So worst case scenario and you are getting too much tension on the extractor, just pull the O-ring off and throw it in a tool box.

I'd go ahead and find some high temp threadlocker. The gas block can get pretty hot and sees a fair amount of vibration.

Beyond getting this rifle dialed in, I'm not going to do much to it but put a sling and light on it and mount a cheap NC star holo sight (45 bucks, lifetime guarantee, day and night settings, red and green reticule, all steel, not bad for a budget AR?).
Click to expand...

The NCStar sight isn't worth the time unless you already have one on hand. I've watched them die on the firing line too many times. Typically the problem is that they don't hold zero; but they just die completely a fair amount of the time too.
 
any tricks to getting the gas block on perfectly straight every time, other than just going slow and making sure? i THOUGHT i had it on perfect last night and it turned out to be a little crooked.
 
Put 25 rds through it today, zero problems. I wouldn't exactly call it a sure thing because the range I was at only allowed a shot per second, but you guys definitely helped me thank you.


I like the fact that it works, but I still want to make sure the gas block is PRECISE on the front end and that I've sealed up the possibility of this happening in the future...especially under use in a time in which the stakes are real...
 
:what: Do not use foaming powder blast on AR's!!!!!!11!!!!!!1!!!!!!!!!!!!!!

While it helped you diagnose a problem here, it tends to work its way under the front sight/gas block and eat the finish under the sight and rust there. Some foaming powder blast type cleaners come with a warning not to use on Ar's. Blast your rifle down with some Clp to get that powder blast off. Just CLP and a brush do fine for cleaning mine. Then I wipe the CLP of the BCG and lube it up with a thicker/stickier oil. Like Mobile1/ATF/STP mixed equally together.

I don't have much experience with gas blocks, but I prefer the clamp on style. I've never had to clean a gastube, never heard of anyone doing that. YHM has/had a clamp on gasblock that was nice. Often the gas block holes are larger than the barrel port.

To make sure the gas block is not blocking the port. Fire alot of rounds. Then mark the gas block and barrel. Remove gas block and check to see if there is marking/errosion/dark round mark on the gas block. If the block is partially blocking the port you'll see where when you remove it. You can either adjust it if its crooked or open up the hole in the gas block. Use the "timing" marks you made before removal as reference.


AR15.com has a good tutorial on building AR's from scratch. AGI also has a good AR15 kit build DVD.
 
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i'm not a fan of set-screw type gas blocks either(doesn't meen they don't work)i just prefer a clamp on just like zerodefect.i've got a Daniel defense clamp on and have had zero issues. as far as indexing it goes you should be able to remove the set screw look through the hole line it up with the gas port then spin the block 90 degrees and voila its index correctly. i wanted to make sure i had mine perfectly level with the receiver.so holding my upper receive with my dpms upper receiver holding fixture in my vise i shimmed my table until the level i had on my receiver was plum(mine is a a3) then i simply put the torpedo level on the gas block and got it plum also and have had zero issues since
 
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