Help me troubleshoot my single shot AR15.

[hlee]

Ok, it is not supposed to be a single shot, but I can't seem to get enough gas to the bolt to get it to eject and chamber the next round.

Build
Aero M4E1 upper and lower
AR 15 Performance 224 Predator Barrel (+2 gas)
+2 gas tube
Odin Works Adjustable gas block
AR15 Performance Titan Bolt
American Defense Manufacturing Premium bolt carrier
JP Silent Capture Spring- H2 with Black spring
Geissele SDE trigger
Assorted other parts required to make a functional rifle

I took it to the range today for the first time. I had a series of loads made from 26.3 out to past 31 grains of CFE223 behind Hornady 88gr ELDM bullets. With the gas full on, I was getting (nearly) zero happening with the bolt until I got to 28.7gr, where the bolt was moving enough to occasionally eject a case. I never got the rifle to chamber a round, but stopped with a pierced primer (30.2gr). The barrel is melonited so it is a bit difficult to see the carbon from the gas port on the journal, but I am including a picture of it.

What I hope you can see is carbon at the gas port mostly dispersed laterally and evenly. This would seem to suggest that the block was square over the gas port. What I can also see, but may be difficult in the picture, is a "fan" of carbon that appears to have been sprayed from the adjustment screw on the Odin Works gas block.

My next step, I think, will be replacing the Odin works block with a non-adjustable block- at least for the time being. That will, at minimum, remove the leakage from an adjustment screw from the equation.

This isn't my first AR15 build (not that I've built a bunch), but it is the first that didn't run like a sewing machine out of the gate. What else should I be looking for. I have the rifle mostly torn down at this point so I can get additional pictures if you think they would help. Thanks.

Oh, velocities ranged from a low of 2724 at the first charge weight up to 3062 at 30.2.

 

[padom]

So if we have that gas block hole over the gas port which from a glance looks good.

1. Have you used air or pipe cleaner or something to ensure air (gas) can properly pass through that Odin Works gas block to confirm its not faulty inside??

2. Did you blow air or push a pipe cleaner or something through that +2 gas tube to ensure its not clogged or faulty?

3. Is it actually a +2 gas tube? or is it too short?

 

[TonyTheTiger]

What size is the gas port? It doesn't look wildly undersized in the pic for what thats worth.

 

[hlee]

So if we have that gas block hole over the gas port which from a glance looks good.

1. Have you used air or pipe cleaner or something to ensure air (gas) can properly pass through that Odin Works gas block to confirm its not faulty inside??

I don't have a can of compressed air on hand, nor any sufficiently long pipe cleaners. However, I just disassembled the adjustment screw on the gas block. Then I shot some gun scrubber through the gas tube/block assembly. It appears to run freely through both.

2. Did you blow air or push a pipe cleaner or something through that +2 gas tube to ensure its not clogged or faulty?

See 1.

3. Is it actually a +2 gas tube? or is it too short?
Yes, it is a +2 gas tube. It was packaged with the barrel from AR15 performance. I also have a rifle length tube on hand and it is shorter than the tube on this gun.

What size is the gas port? It doesn't look wildly undersized in the pic for what thats worth.
0.096"

 

[roostercogburn98]

Would you consider this a high pressure round? Odin Works says some of their adjustable gas blocks aren’t designed for high pressure rounds

 

[hlee]

Would you consider this a high pressure round? Odin Works says some of their adjustable gas blocks aren’t designed for high pressure rounds

The 6.5 Grendel (parent case) isn’t generally regarded as a high pressure round, but...

 

[roostercogburn98]

Just food for thought. Cartridge is supposed to sling stuff at 3100 plus so maybe it is too much for that Odin Works. Contact their cs and see what they think.

 

[TonyTheTiger]

.096 seems plenty sizeable. New BCG? If used I'd check gas key tightness and gas rings. Like padom said check all the various holes for flow.

 

[redneckbmxer24]

Did you verify the gas tube is the right length and sliding back into the gas key? Verify gas rings are good?

 

[Rocketvapor]

0.096" for a +2, 22" should allow for gas adjustment.
The Odin works might not hold up to high pressure rounds but sure should pass gas.
Got carbon on the back of the bolt from firing?
Got carbon on the pin leaking out the back of the bolt from a mismatch in diameter?
Got carbon in the upper?

 

[hlee]

Did you verify the gas tube is the right length and sliding back into the gas key? Verify gas rings are good?
The gas tube is the correct length. The bolt and rings are new, and the bolt does not collapse freely into the carrier as it might if it had worn rings.

0.096" for a +2, 22" should allow for gas adjustment.
The Odin works might not hold up to high pressure rounds but sure should pass gas.
Got carbon on the back of the bolt from firing?
Yes
Got carbon on the pin leaking out the back of the bolt from a mismatch in diameter?
The firing pin? Yes, there is some carbon on it, but no more than I have seen on any other.
Got carbon in the upper?
Yes

From what I can tell, there is carbon in all of the right places, so there is SOME gas getting to the bolt. I do have ejection sometimes, but not enough to chamber the next round.

At this point I have a few working hypotheses.
1) The gas block is leaking too much gas due to the pressure of this round.
A non-adjustable gas block is easy and cheap.
2) The SCS is too heavy/strong. This would seem to be contrary to 1, but it was bought as a builder kit, and I can put in the weakest spring to test this. I also have a standard spring/buffer setup that I can swap in, as well as a standard weight SCS in another rifle. At least I remember it being a standard weight, I'll need to check.
3) The bolt/barrel are brand new and need to wear in. I can put a movie on the TV and mindlessly open and close the action a few hundred times.

I can swap in and out a lot of parts, as I have 2 6.5 grendels sitting in my gun safe. The only thing that I cannot swap in is a bolt, as the Titan bolt has a unique lug geometry not shared by the others.

One other observation, there seems to be a lot of carbon on the tip of the gas tube, much more than I see in my other rifles. The picture below shows the comparison to a straight rifle length tube. You can also see the carbon on the tip of the +2 tube.

The brass was also dirtier than I expect, though this is my first experience with CFE223 and I have read that it can be dirty. The brass almost look like they've been fired from a supressed rifle. Could my bolt and carrier be experiencing sufficient resistance to prevent proper function? They were well lubed (mobil 1 synthetic) but also brand new...

 

[Tim_WNC]

Just throwing this out there as I am prone to doing stupid shit...

The Odin Works AGB that I have uses 2 screws. An inner screw that actually adjusts the gas which is then topped by a set screw. Are you certain you've actually adjusted the gas, or have you just messed with the set screw?

 

[hlee]

Just throwing this out there as I am prone to doing stupid shit...

The Odin Works AGB that I have uses 2 screws. An inner screw that actually adjusts the gas which is then topped by a set screw. Are you certain you've actually adjusted the gas, or have you just messed with the set screw?

Thankfully, the gas adjustment screw is big, obvious, and in the front of the block. It was full open- I even went and found the instructions on line while at the range (thank you smart phone), because I am also occasionally prone to do stupid shit...

 

[TimK]

Is the gas tube correctly aligned with the gas key? Gas block not perfectly aligned can cause some binding.

 

[hlee]

Is the gas tube correctly aligned with the gas key? Gas block not perfectly aligned can cause some binding.

Well, the gun is pretty well torn down at this point. But, when it was assembled, the bolt and carrier would slide home (but not lock) under their own weight, by simply tilting the upper receiver enough to get them moving...

 

[DRAM40A1]

I have a 224 Valkyrie that will only cycle with a 3 oz carbine buffer and a semi auto carrier. Could it be that the H2 is too much mass for the available gas?

 

[Lawless]

If the port in the barrel is free and open and the gas tube unobstructed it just about has to be the block.

 

[dang472]

I battled my first Valkyrie build with low gas/barely cycling issues. 20” barrel with +2 gas. Tried a low mass bolt, low power buffer spring, standard gas block and adjustable one from SLR. I would sometimes get a few rounds to cycle but nothing reliable. I finally got pissed and started opening the gas port. Also measured the port in relation to the gas block shoulder on the barrel. I determined the guy who did the barrel either drilled the port in the wrong spot or the shoulder wasn’t machined back far enough to allow the gas block to line up over the hole completely. If you have another barrel to compare to, measure the centerline of the gas port from where the gas block seats against the shoulder.
I still have the feeling the Valkyrie isn’t the high pressure wonder round it was originally marketed as that needs a +2 gas system out of a 20” barrel. 22-24” sure, but I bought a 20” Wilson Combat rifle gas barrel to replace this disaster of my original barrel and it cycles great and is soft shooting with the JP SCS.

 

[hlee]

Looks like we are reaching a consensus that the gas block is, at minimum, a suspect. I'm going to grab a non adjustable block and switch it out. This is a wild cat cartridge, so I can't go to Walmart and grab a box of ammo to test, and my reloading/work bench looks like my garage barfed on it, so I'll be slow to update this thread. But, this it the rifle I want to match shoot with this year, so I will be getting it working...

 

[padom]

My 224V AR was finicky with gas as well. I came to the conclusion it did not need a +2 gas length. It was weird, 80 ELD would run great, 88 ELD would not....They would not cycle reliably. Had to open gas all the way open and still not 100%. Had to drop weight and change to lower weight springs in my SCS. Sounds like your having similar issues.

Have lighter 77gr/80gr bullets to test with ??? If so, load up Hornady 80 ELD or 80 Amax with 25gr 8208XBR. 2895 SD 3 and sub 0.5moa and cycles reliably. If you dont have 8208XBR, load up 24.8gr of H4895 with a 80 ELD. My COAL was 2.287". This also cycled 100% reliably.

When I got the barrel, I started off testing with 80gr bullets, but when I switched to testing those 88's in my 22" Rainier Ultramatch +2 gas they just didnt cycle 100% with all gas wide open. Forgot about this, looking at all my notes and data now after going over your issues and what you have done. I was running a JP 6.8/224V bolt, Superlative Arms AGB, +2 gas tube, and SCS spring. That SCS was tuned for the 80 Amax and 80 ELD and ran super accurate and 100% reliable. Then switched over to 88 ELD load workup and cycling reliability went to shit just like your experiencing.

 

[sam4886]

Start with the simple stuff. Did you ever get the buffers/springs swapped around to test? That's where I would start.

I've got a 6mm predator and I'm running all low mass stuff with an AGB no problem.

 

[dang472]

Glad to see (unfortunately) that others have had +2 gas length issues. I thought I was crazy because when the Valkyrie came out, it was almost universally accepted that it needed extended gas.
Here’s my thread battling these same issues in 2018.

https://www.snipershide.com/shootin...n-with-extended-gas-for-the-valkyrie.6901678/

 

[hlee]

My 224V AR was finicky with gas as well. I came to the conclusion it did not need a +2 gas length. It was weird, 80 ELD would run great, 88 ELD would not....They would not cycle reliably. Had to open gas all the way open and still not 100%. Had to drop weight and change to lower weight springs in my SCS. Sounds like your having similar issues.

Have lighter 77gr/80gr bullets to test with ??? If so, load up Hornady 80 ELD or 80 Amax with 25gr 8208XBR. 2895 SD 3 and sub 0.5moa and cycles reliably. If you dont have 8208XBR, load up 24.8gr of H4895 with a 80 ELD. My COAL was 2.287". This also cycled 100% reliably.

When I got the barrel, I started off testing with 80gr bullets, but when I switched to testing those 88's in my 22" Rainier Ultramatch +2 gas they just didnt cycle 100% with all gas wide open. Forgot about this, looking at all my notes and data now after going over your issues and what you have done. I was running a JP 6.8/224V bolt, Superlative Arms AGB, +2 gas tube, and SCS spring. That SCS was tuned for the 80 Amax and 80 ELD and ran super accurate and 100% reliable. Then switched over to 88 ELD load workup and cycling reliability went to shit just like your experiencing.

Thanks for this. I have 8208XBR, but 75gr is the biggest bullet I can source locally. Sounds like the 80s ran with the heavy SCS, correct?

Start with the simple stuff. Did you ever get the buffers/springs swapped around to test? That's where I would start.

I've got a 6mm predator and I'm running all low mass stuff with an AGB no problem.

Not yet, this will be more of a saga I am afraid. I can only get out to the range occasionally, so the "guess and check" method is slow.

That said, of all the things that I can do, the most difficult to swap around at the range is the gas block. This will be my first step. From there, I'm headed to the range with a bag of parts- pulled from other rifles (buffer/spring from one rifle, SCS from another, bolt carrier from a known good rifle, etc). Hopefully I can cobble together a working rifle from the parts of a few others, and from there I can diagnose the problem bit. And, I'll take Padom's suggestion of backing off on the bullet weight with the next set of loads. I've also read that the speed you can achieve with the 80s out performs the BC of the 88s anyway...

 

[padom]

Thanks for this. I have 8208XBR, but 75gr is the biggest bullet I can source locally. Sounds like the 80s ran with the heavy SCS, correct?

75gr will be fine for your testing. 77smk,, 77 TMK, 75 ELD-M, etc.

No, I dont run SCS Heavies in small frame AR's. Never needed to, just in my large frame 6.5cm gassers I run a SCS Heavy with Yellow Spring. In 224V with the +2 gas I have SCS with the steel weights and white spring.

 

[Constructor]

Ok, it is not supposed to be a single shot, but I can't seem to get enough gas to the bolt to get it to eject and chamber the next round.

Build
Aero M4E1 upper and lower
AR 15 Performance 224 Predator Barrel (+2 gas)
+2 gas tube
Odin Works Adjustable gas block
AR15 Performance Titan Bolt
American Defense Manufacturing Premium bolt carrier
JP Silent Capture Spring- H2 with Black spring
Geissele SDE trigger
Assorted other parts required to make a functional rifle

I took it to the range today for the first time. I had a series of loads made from 26.3 out to past 31 grains of CFE223 behind Hornady 88gr ELDM bullets. With the gas full on, I was getting (nearly) zero happening with the bolt until I got to 28.7gr, where the bolt was moving enough to occasionally eject a case. I never got the rifle to chamber a round, but stopped with a pierced primer (30.2gr). The barrel is melonited so it is a bit difficult to see the carbon from the gas port on the journal, but I am including a picture of it. View attachment 7220596
What I hope you can see is carbon at the gas port mostly dispersed laterally and evenly. This would seem to suggest that the block was square over the gas port. What I can also see, but may be difficult in the picture, is a "fan" of carbon that appears to have been sprayed from the adjustment screw on the Odin Works gas block.

My next step, I think, will be replacing the Odin works block with a non-adjustable block- at least for the time being. That will, at minimum, remove the leakage from an adjustment screw from the equation.

This isn't my first AR15 build (not that I've built a bunch), but it is the first that didn't run like a sewing machine out of the gate. What else should I be looking for. I have the rifle mostly torn down at this point so I can get additional pictures if you think they would help. Thanks.

Oh, velocities ranged from a low of 2724 at the first charge weight up to 3062 at 30.2.

Those barrels are ported to run correctly with full power loads with standard springs and buffers so it may not lock back when using a starting load that produces 5-10000 psi less. For every 1gr of power down from full power you will lose 4-5000psi. Heavy buffers and strong springs will also slow the carrier so your captured spring and heavy buffer may be whats slowing it down. If you have checked for gas leaks and there are none and you have found an accurate load at a lower pressure that you want to use or want to use that spring and buffer and it does not cycle you can open up the gas port a little. All it takes is a hand drill. Do not use carbide bits, they break too easy. Spin the bit fast with very little to no pressure. Completely opposite of how you would try to drill through a piece of plate, the hole is already there. It may take a .098 or .101 bit.
ETA- Around 30gr maybe 30.5 gr with an 80gr bullet will be near max. I had loose primer pockets with 31gr using Lapua brass. Norma brass will handle more pressure and last longer.

 

[hlee]

Those barrels are ported to run correctly with full power loads with standard springs and buffers so it may not lock back when using a starting load that produces 5-10000 psi less. For every 1gr of power down from full power you will lose 4-5000psi. Heavy buffers and strong springs will also slow the carrier so your captured spring and heavy buffer may be whats slowing it down. If you have checked for gas leaks and there are none and you have found an accurate load at a lower pressure that you want to use or want to use that spring and buffer and it does not cycle you can open up the gas port a little. All it takes is a hand drill. Do not use carbide bits, they break too easy. Spin the bit fast with very little to no pressure. Completely opposite of how you would try to drill through a piece of plate, the hole is already there. It may take a .098 or .101 bit.
ETA- Around 30gr maybe 30.5 gr with an 80gr bullet will be near max. I had loose primer pockets with 31gr using Lapua brass. Norma brass will handle more pressure and last longer.

So, it pays to remember what you have working in other- similar- rifles. I have a 6.5 grendel that I thought had a heavy SCS in it. As it turns out, it is running perfectly with the standard SCS (3 steel weights) and the white (lightest) spring. In the problematic 224 Predator, I have a heavy SCS (1 steel, 2 tungsten weights) and the black spring (one up from lightest). The 6.5 grendel is a 22" barrel with rifle length gas. The 224 Predator is a 22" barrel with +2 rifle length gas.

I hate changing multiple variables at once, but I also hate driving out to the range more often than necessary. I'll change the block (possible source of gas leak), change the spring in the heavy SCS to the lightest one (too much spring pressure?), and pack the standard SCS as well (too much buffer weight?). I can source 75gr projectiles locally, so I will work up a series of loads with that bullet and CFE223 or 8208XBR, maybe both. The goal is a rifle that functions at 100%. I'll tweak loads, bullet weights- maybe revisit an adjustable gas block- later.

 

[padom]

So, it pays to remember what you have working in other- similar- rifles. I have a 6.5 grendel that I thought had a heavy SCS in it. As it turns out, it is running perfectly with the standard SCS (3 steel weights) and the white (lightest) spring. In the problematic 224 Predator, I have a heavy SCS (1 steel, 2 tungsten weights) and the black spring (one up from lightest). The 6.5 grendel is a 22" barrel with rifle length gas. The 224 Predator is a 22" barrel with +2 rifle length gas.

I hate changing multiple variables at once, but I also hate driving out to the range more often than necessary. I'll change the block (possible source of gas leak), change the spring in the heavy SCS to the lightest one (too much spring pressure?), and pack the standard SCS as well (too much buffer weight?). I can source 75gr projectiles locally, so I will work up a series of loads with that bullet and CFE223 or 8208XBR, maybe both. The goal is a rifle that functions at 100%. I'll tweak loads, bullet weights- maybe revisit an adjustable gas block- later.

2 tungsten is way too much for that setup. Just put that SCS with white spring and 3 steel weights in the 224 Predator, probably just put your odin works gas block back on as well and leave wide open. With those lighters 75 gr loads with 24.5-25gr of 8208 I bet youll be closing that gas block some and be g2g.

 

[Blutroop]

I had similar problems when I built a +3 17 Remington 26”. I had a knockoff scs, got a lightweight bolt, drilled gas hole bigger, marked it for perfect realignment, (I drilled my hole slightly cracked on a drill press in a haste to shoot) and finally got it to eject every time. Still doesn’t lock back last round though. Hang in there. If none of your standard parts will help then get a lightweight buffer and bolt. You could always drill a hole at rifles length and plug the +2 hole. Good luck

 

[Snuby642]

I have a new reciver and barrel 223, the first groups failed lock back and had feed issues.

Bcg and lower well used and reliable.
Buffer was h2.

Compleate cleaning and lube has the bcg moving freely and swap to a mill spec original buffer.

The stoner barrel may be drilled to work with a standard buffer.

That will be a first in many years for me.

Range asap.

 

[hlee]

Update- This took a while because I was waiting on a new scope. Leupold got my Mk5 to me on Monday and I went to the range today. Prior to that I also ordered 2 steel weights from JP enterprises for the silent capture spring. And, I made sure the gas block was wide open. For loads, I had 10 loaded with 27.8 gr CFE223 and 88gr ELD-Ms and a series from 27.3 gr to 30 gr CFE223 with 75 gr ELD-Ms. Everything fired and cycled perfectly. The rifle fed, fired, cycled, and locked back on an empty mag every time. It appears I have 2 nodes to play with using the 75 gr bullets so I'll load some more and decide between the 2. According to JBM Ballistics the difference in wind is 0.1 Mil at 800 yards so I'm leaning toward the lower node- where I typically shoot, the ranges are given. But, the difference in drop at that range is 1 mil. I'll stretch them out to 600 yards (the furthest I have locally) and see who wins. At any rate, thanks to everyone that chimed in on this thread.