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Discussion Starter · #1 ·
So my newly built AR is having some feeding issues. I originally thought it was the Orlite mags I was using but after yesterday it seems to be an ammo/under gassed issue. My issues are double feeds/jams and possible short strokes. This has been experienced with American Eagle (brass), and Tula (steel case). I've fired a bunch of Remmington with no issue.

Yesterday while out plinking, once I switched to the Tula ammo virtually every other shot was either a doublefeed/jam or short stroke. There were two other newly built AR's being shot which had no issue with the same ammo. For troubleshooting I tried different mags (Orlite, USGI) and also swapped my BCG with another shooter. I should also note that they have the same BCG and experienced no issues.
So my question is WHY is this happening and WHAT can I do about this? I refuse to believe that I just plain can't run this ammo when the other guns right next to me ran fine. Internally, what is different in my gun that may be causing the issue?

All-Star upper
All Star LPK
All Star buffer
Spikes lower
Spikes BCG
DD 16" chf barrel
Midwest low profile gas block

Thanks,
Daryl
 

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I had a short stroke issue after a build and it ended up that my buffer tube was way out of spec. It was too short inside and would bottom out and jam or not cycle the next round. I also forgot to put the roll pin in the gas tube once and it was short stroking. Hope this helps.
 

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If you bought a complete upper / AR inform the manufacturer.


If you built it you need to make sure mil specs parts are used, then here some simple points to inspect.

From easier to more complex.
1- Assume you have a 5.56 barrel (not 223rem) properly ported. Just to discard potential chamber issues.
2- Is the gas block properly installed. Failure to align with the gas post will cause loss in pressure.
3- Is the gas block leaking? typical problem in some troy and other blocks, mostly set screw type.
4- Check the gas rings in the bolt make sure the notches do not align letting the pressure out.
5- Cancel the port by moving the block forward and shoot each one of those rounds and open the bolt manually to see if there is substantial resistance to open the bolt. That will point to a different kind of problem chamber related.
6- If all the above fails you need to consider point 1 and if the porting is actually enough. You do not want too much or too little.
7- last thing is to buy a heavier buffer and/or lighter spring. As someone mentioin make sure your tube is up to spec too.

I hope this helps.
 

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Discussion Starter · #5 ·
what kind of stock/buffer tube and buffer is it?
mill spec carbine length buffer tube from All Star Tactical, Magpul MOE stock.

For what it's worth. When I installed my gas block, I have it set about a 1/32" away from touching the stop collar on the barrel. I read somewhere that it should not actually touch as it would be too far back. Is that worth persuing or is that OK?
 

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mill spec carbine length buffer tube from All Star Tactical, Magpul MOE stock.

For what it's worth. When I installed my gas block, I have it set about a 1/32" away from touching the stop collar on the barrel. I read somewhere that it should not actually touch as it would be too far back. Is that worth persuing or is that OK?
No it is not ok. You need to take your calipers and a pen and put it exactly where it needs to be. Eyeballing is not the best in this cases as the gas block that is not mil spec might be anywhere. After having fired already and if this is not aligned you might see already a half moon around the port that will tell you that you are off. Check this and the gas rings in your bolt before anything else. Also any leaking.
 

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Discussion Starter · #7 ·
No it is not ok. You need to take your calipers and a pen and put it exactly where it needs to be. Eyeballing is not the best in this cases as the gas block that is not mil spec might be anywhere. After having fired already and if this is not aligned you might see already a half moon around the port that will tell you that you are off. Check this and the gas rings in your bolt before anything else. Also any leaking.
Thanks for the advise. I'll try and do that tonight. I'm completely new to AR's, can I assume that the half moon you're referring to would be carbon build up favoring one side of the gas port on the barrel? I did check the gas rings and they seem to be fine (they're staggered)
Also, what am I looking for when checking for leaks?

Thanks,
 

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Who installed the gas block, and is everyone absolutely postive its indexed correctly?

If by 'double feed' you mean 2 live rounds popping out, that is almost exclusively in the relm of magazine issues.
If you meant one expended and one live wadding up in there, that's generally a cycle issue that can be related to gas restriction, buffer weight, spring rate, or some combination of same.

*We're going to say that based on the barrel info that the porting is indeed the correct size and not configured to over gas.

You say Allstar buffer, but what weight is it if used in a carbine configuration? (carbine, H, H2 etc.)
Who supplied the buffer spring?
Was it the correct spring for the receiver extension type? (as in not a rifle spring in a carbine tube or vice versa)

BTW, swapping carriers, firing pins, cam pins and firing pin retaining pins is more or less acceptable behavior.
Swapping actual bolts between barrels/firearms isn't all that high on the 'good plan' list though.
Yes, they should all be in tolerance and thus interchangeable with each other when brand new but as wear over time takes its toll, the more exclusive a bolt is to its given barrel and vice versa.
You can put a brand new bolt in an old barrel to try and recover from headspace issues, but you never want to mate a new barrel to an old bolt (they get changed as a set in that instance)

Technically the cam pin shouldn't be swapped either as the wear pattern from one BCG will be subtly different than that of the one it goes into and can result in a timing change to the lock/unlock part of the show.
It wouldn't create a catestophic incident, but could indeed effect the overall function of the firearm to the point of cycling issues coming up if things are way out of whack.

EDIT:
Damn, typing slow puts me behind the power curve yet again....
 

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Speaking of carbon marking, check around the base of the gas key on the carrier.
If its leaking there will be carbon buildup along the seam where key and carrier mate.
Also try to twist or wiggle it (not the screws but the key itself) to ensure that it is on thier tight to begin with.

AFA the gas block, look at the bottom and you'll find a hole where they drilled through to make the port in the top.
Put a bit of masking tape around the barrel aft of the gas block shoulder.
Put the block on the barrel upside down and align that hole with the port in the barrel that you can now see.
Mark the the tape with a thin pencil/pen line to indicate where the center of the port is.
Reorientate the block to its correct position.
Butt it up against the shoulder on the barrel.
Align the center of the gas tube hole with the index mark on the tape.
Lock it down.
Remove tape after confirming that thinjgs stayed in place during tightening.
 

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A little bit of leaking (carbon residue) around the gas tube is ok. Too much is not. So that is why I told you to check the rings because if you start adding things up then you are loosing gassy gas everywhere. Eventually some leaking from the tube might stop form the carbon itself and specially if you shoot russian puffins that assure a steady supply of soot.
Yes the half moon will be 'printed' around the barrel port from the already fired system.
 

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Discussion Starter · #12 ·
Thanks all for the advise. I can't answer as to buffer weight, spring length. I'll get measurements and pics on those tonight. Gas block may be a pain as my muzzle break is welded on. Hopefully I'll be able to get a better idea by looking at carbon patterns on the barrel.

Thanks,
Daryl
 

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Speaking of carbon marking, check around the base of the gas key on the carrier.
If its leaking there will be carbon buildup along the seam where key and carrier mate.
Also try to twist or wiggle it (not the screws but the key itself) to ensure that it is on thier tight to begin with.

AFA the gas block, look at the bottom and you'll find a hole where they drilled through to make the port in the top.
Put a bit of masking tape around the barrel aft of the gas block shoulder.
Put the block on the barrel upside down and align that hole with the port in the barrel that you can now see.
Mark the the tape with a thin pencil/pen line to indicate where the center of the port is.
Reorientate the block to its correct position.
Butt it up against the shoulder on the barrel.
Align the center of the gas tube hole with the index mark on the tape.
Lock it down.
Remove tape after confirming that thinjgs stayed in place during tightening.
Good point, I do not see many keys out of wack but there are some out there.
Any key should be squared, tight and properly stacked.

Some gas blocks anyway are plain crap. I have seen several troys that had to be put in the trash can. All set screw.
 

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] Gas block may be a pain as my muzzle break is welded on
You don't have to remove it entirely to do the port alignment thing if that's what you're meaning.
Just loosen it and twist it around 180.

Some gas blocks ... set screw.
Best thing for those is to drill small dimples in the bottom of the barrel to engage the screw tips.
I gravitiate toward the clamp style myself, but only because I don't build enough barrels to warrant purchasing the taper reamer needed for pin on types.
 

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Discussion Starter · #15 ·
Okay so I tore her down tonight.
1. My brother (flysh22) spoke to Mike from All Star and he confirms that the gas block should sit against the shoulder of the barrel.
2. Gas tube end to end is 9 3/4", buffer spring is 11", buffer weighs 2.967 oz. I believe that these are all standard/carbine appropriate.
3. Gas block was approx 3/64" ahead of the shoulder of he barrel.
4. Gas key is rock solid and properly alligned onto carrier.

So here are some pics I took of my original placement. It seems that even though you can see that the hole from the gas block is slightly off center from the hole in the barrel, it's large enough where it seems to be within spec as it fully encompases the hole. I have since moved the gas block as far back as it will go. Hopefully I can test in the next couple of days and report back.
Please take a look at the pics and tell m how it looks (original configuration).

Thanks,
Daryl
 

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Pic #1: shows some distinct gas leakage blowby on the tube
Pic #3: what's up with the hole looking all distorted as opposed to how crisp in #5?
 

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Discussion Starter · #17 ·
Pic #1: shows some distinct gas leakage blowby on the tube
Pic #3: what's up with the hole looking all distorted as opposed to how crisp in #5?
Pic #1. I did notice some carbon build up on the right side of the tube. Is that enough to cause concern? Is there a fix without replacing parts?
Pic #3 was just right after gas block removal. Pic #5 was just cleaned up. You can see in the pic that the gas hole on the barrel was totally covered by the port in the gas block.
 

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What about your gas rings on the bolt? Your blow by on gas tube at the gas block isn't completely unusual. I have seen worse on rifles that still fire and cycle just fine.

Gas block should certainly sit back against shoulder, pic shows that from the carbon printing, but shows that it's close.

Also, assemble the rifle without the buffer and buffer spring and cycle the BCG(via charging handle) and make sure there is no binding of the bolt carrier in the tube or upper. You may need to give the rifle a smack on the butt(LOL) with a rubber mallet to move the carrier forward without the force of the spring acting against it.
 

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What picture 1 looks to me is some leaking from the gas tube. When I put the gas tube in and before it goes all the way I put a drop of locktite blue but my gas blocks are so tight that they barely bleed or stop right away.
What picture 3 says is that the block might not be sealing properly. the gas block doesn't look too tight to me but I might be wrong. I don't know why folks take the risk with set screws like that. If it was me I would have a quality clamp on block there.
Anyway that might not be the 100% of the reason so move on down the pipe. Make sure you have a clean tube and look beyond in the gas key etc...
Also try the other steps I and others told you. ...or simply have the gun inspected by a pro.
do not locktite anything until you are done debugging. you might need to do step 5 above.
If you want to stop by GCL on Saturday I am happy to take a look. We will be there after the leagues.
 

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There was definately some blowback. Realign and tighten everything down.
Hopefully with the g/b slid back tight to the collar, it will cut down on the blowback.
Plus your gas tube will be seated into the gas key better, both of which will help.
 
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