AR-15 Failure to extract and accuracy problems HELP! *** UPDATE POST 26***

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zombiedfens

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I Put together my first AR15 awhile back, I have issues regarding accuracy that i cant seem to iron out, I'm all over the target at 100 yards and at 25 yards my groups should be alot better I think. I have pictures below, these were fired off a bi pod and a homemade rear bag I placed under the butt stock. Specs of rifle Below

Aero Precision Lower
Daniel Defense LPK
Questar Buffer tube, spring, buffer and stock package
DPMS A3 Upper
LMT FA Bolt and Carrier
YHM FF Quad Rail
16.5 Inch SJ Hardware Barrel Gas Nitride Treated (5.56 Chamber, 1/7 twist, CarbineLength Gas System )
Low Profile Gas Block
Burris PERP Quick release optics mount
Burris Full Field II 3x9x40 Scope

Im also getting a failure to extract/feed, i have pictures of that below as well. I have fired several different brands of ammo thru this rifle. Remington UMC, Norinco, AE black box, AE red box and AE 62grain. groupings with all ammo tried is identical to below. I'm am at a loss as to what the problem could be.

Could it be the Barrel? i read something about S&J barrels being "overgassed" or having the gasport larger then normal?
Could this be something to do with my FF handguard setup?
Could the Lower be affecting things at all?

It is completely possible that the issue could be me so if anyone in the Winnipeg area would be interested in meeting up at a range and giving my rifle a shot ( my ammo of course ) I could rule either me or the rifle out as being the problem.



100 Yard Target

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25 Yard Target

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Failure to extract/feed

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Any assistance at all would be greatly appreciated.

Regards,

Craig
 
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The first things I would check are that the scope is indeed mounted perfectly solid, and that the barrel nut is fully torqued.
If both of those appear to be ok I might try another optic, then look into testing another barrel.

Why is there grease? or peanut butter between your upper receiver and barrel nut?
 
In the past S&J barrels tended to be overgassed (they may have corrected that as of more recently) but that in itself wouldn't necessarily cause your issues.

A loose extension would.

There was a batch of S&J barrels that had the nitriding done after the barrel extensions were installed and it was causing them to come loose.

Grab the end of the barrel in one hand and the upper in the other and twist back and forward. There should be no noticeable movement.
 
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I'm Pretty sure the scope is mounted good, unfortunately i don't have iron sights to verify that. any other way i could verify this?

The barrel nut is the aluminum nut from the Yankee hill machine free float rail, they are not supposed to be torqued on with a torque wrench ( as per the person i talked to at YHM ) it was screwed on until tight and then tightened further until the next gas tube hole lined up with the upper receiver. Should i have done this different?

The grease between the upper and barrel nut was from the grease i had originally placed on the threads of the upper receiver, I remember reading that a little moly grease doesn't hurt when screwing down the barrel nut.
 
*MALICE* said:
Check to make sure the barrel extension is not loose. There was a batch of S&J barrels that had the nitriding done after the barrel extensions were installed and it was causing them to come loose.
Click to expand...

How loose are we talking? i did check this previously as this was one of the early nitrided barrels and there was not any looseness i could detect by hand.
 
zombiedfens said:
How loose are we talking? i did check this previously as this was one of the early nitrided barrels and there was not any looseness i could detect by hand.
Click to expand...

Was that before or after you installed it? You likely would not have noticed it pre-installation, or even after you tightened the barrel nut. After firing it a couple times it could then come loose.

If it's the issue now, you will notice it by twisting the barrel by hand now

It may not be the issue but it's a good place to start.
 
If you don't have a muzzle-widget on the end of the barrel and your gas block is clamped or set-screwed on; remove the gas block and pull the gas tube out of the receiver, then turn the barrel. If it unscrews.............

Added - I just noticed you have a muzzle -widget. See if you can slide the gas block (and gas tube) off enough to try and rotate the barrel by hand.
 
zombiedfens said:
I'm Pretty sure the scope is mounted good, unfortunately i don't have iron sights to verify that. any other way i could verify this?

The barrel nut is the aluminum nut from the Yankee hill machine free float rail, they are not supposed to be torqued on with a torque wrench ( as per the person i talked to at YHM ) it was screwed on until tight and then tightened further until the next gas tube hole lined up with the upper receiver. Should i have done this different?

The grease between the upper and barrel nut was from the grease i had originally placed on the threads of the upper receiver, I remember reading that a little moly grease doesn't hurt when screwing down the barrel nut.
Click to expand...

Grab the rifle with one hand and grab the scope with the other. if it moves, it's loose... :p

I've never heard of YHMs tightening process, but if they use an aluminum nut, it is probably best to follow their advice. Although, it seems possible to me that greased threads may allow the barrel nut to loosen while firing.

I forgot to mention the loose barrel extension that someone reported earlier this year. It could be the culprit as well.
 
*MALICE* said:
If you don't have a muzzle-widget on the end of the barrel and your gas block is clamped or set-screwed on; remove the gas block and pull the gas tube out of the receiver, then turn the barrel. If it unscrews.............

Added - I just noticed you have a muzzle -widget. See if you can slide the gas block (and gas tube) off enough to try and rotate the barrel by hand.
Click to expand...

I removed the muzzle break to rule that out as a problem, When i get home tonight I'm going to check the scope for looseness and check to see if the barrel extension is loose. My understanding of how the barrel extension, the indexing pin and the gas port line up would mean that i would need to send the barrel into S&J for repair or replacement correct?
 
zombiedfens said:
I removed the muzzle break to rule that out as a problem, When i get home tonight I'm going to check the scope for looseness and check to see if the barrel extension is loose. My understanding of how the barrel extension, the indexing pin and the gas port line up would mean that i would need to send the barrel into S&J for repair or replacement correct?
Click to expand...

While some companies drill into the threads to install the indexing pin (doing so won't necessarily prevent an extension from coming loose) the pin's sole purpose is to index the barrel.

Realistically, if the extension were loose, and you torqued it to spec, it's possible (likely) the gas port would be misaligned.

So, yes, if the extension is loose, you send the barrel back to S&J for replacement/refund. They're pretty good for stuff like that from what I hear.

I wouldn't expect your muzzle brake to be causing the issue. While if it were misaligned it could cause the bad accuracy (rounds kissing it as they exited the barrel), it's unlikely to be causing the FTE/FTF issues. Check for copper marks in your brake just in case.
 
I just looked over my email. I got that barrel end of July/beginning of august in 2011. maybe it is one of the affected barrels. I will report back tonight!
 
Scope seems to be mounted solid and i didn't notice any movement of the barrel, however i did email simon at SJ hardware and mentioned when i purchased the Barrel. He immediatly requested that i ship him my upper receiver so he can have a look. that guy got back to me fast. Hopefully everything will work out now.
 
zombiedfens said:
The barrel nut is the aluminum nut from the Yankee hill machine free float rail, they are not supposed to be torqued on with a torque wrench ( as per the person i talked to at YHM ) it was screwed on until tight and then tightened further until the next gas tube hole lined up with the upper receiver. Should i have done this different?

The grease between the upper and barrel nut was from the grease i had originally placed on the threads of the upper receiver, I remember reading that a little moly grease doesn't hurt when screwing down the barrel nut.
Click to expand...

I personally think this is your issue here, hand tight then next hole for a barrel nut isn't tight enough.
My routine (with or without torque wrench) is first to seat the barrel. Make sure you have a proper upper receiver vice block. Use your grease that's fine, then tighten nut firmly with barrel nut wrench, at least one grunt tight. Mark the top of the nut with a marker at 12 o'clock. Now back it off and loosen it up then tighten again to one grunt. Repeat this process 2 more times. Now back off the nut, and tighten to one grunt and see where it lines up with the gas tube....don't back it off this time, you want to go to the next hole now and feel free to use up to 3 grunts to get it there. You will probably find you are 2 to 3 holes past your initial mark you put at 12 o'clock now.....that's good enough, put er together now.
 
Hitzy said:
I personally think this is your issue here, hand tight then next hole for a barrel nut isn't tight enough.
My routine (with or without torque wrench) is first to seat the barrel. Make sure you have a proper upper receiver vice block. Use your grease that's fine, then tighten nut firmly with barrel nut wrench, at least one grunt tight. Mark the top of the nut with a marker at 12 o'clock. Now back it off and loosen it up then tighten again to one grunt. Repeat this process 2 more times. Now back off the nut, and tighten to one grunt and see where it lines up with the gas tube....don't back it off this time, you want to go to the next hole now and feel free to use up to 3 grunts to get it there. You will probably find you are 2 to 3 holes past your initial mark you put at 12 o'clock now.....that's good enough, put er together now.
Click to expand...

Are those metric or imperial grunts?



OP- There is one thing kind of nagging at me. In one of the pictures, it almost looks like the barrel extension is too far away from the ejection port. Now, it could totally just be the angle/shadows.......but it wouldn't hurt to check.
 
When your brass does eject, where is it going?
8-10' away is ideal, if its plunking short, you're not getting enough gas, if its lobbing them far, then over gassed. Also at what angle are they ejecting, forward, to the side or to the rear?
 
Looking at the photos, the fired cases seem to have been extracted, but not cleanly ejected. Extraction and ejection are related. Is the rifle consistently extracting, but failing to eject?
 
The Brass is ejecting at 1 o'#### and 3 o'clock ( asuming the end of the barrel is 12 o'clock )

The rifle is consistantly extracting, but appears to be failing to extract. in that picture a fresh round gets stripped from the magazine and is usually part way or all the way into the chamber
 
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