I recently got a new ballistic advantage barrel for my ar. 18 inch spr profile rifle length gas system. I’m running a sprinco green rifle length buffer spring. I also have a superlative arms adjustable gas block. The issue I’m having is that when I fire it’s not picking up the next round. Ejection is fine but I have to run the charging handle every time I fire. I assume the issue is being under gassed. Any advice on a different gas block that could help the issue or is it worth having a smith open up the gas port on the barrel. Not sure what the solution is here any advice would be appreciated.
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Gunsmithing AR issue need some advice
- Thread starter Altoonabcm157
- Start date
I have had 3 superlative arms adjustable gas blocks. If it is adjusted correctly therhould be no issue.
I and my buddies all have 12.5 and 18” Grendel’s. All with ballisticadvantage barrels and superlative arms gas blocks.
Not saying it’s impossible.... but 10/10 AR malfunctions are operator/assembler induced.
Tried multiple mags??
is the gas block all the way to one side? (Ran out of adjustment)
where is the ejection 1-6 o’clock?
is the gas block on straight?
is it tight?
what are the other component?
who put it together?
what ammo. What cartridge?
Need some more info.
I and my buddies all have 12.5 and 18” Grendel’s. All with ballisticadvantage barrels and superlative arms gas blocks.
Not saying it’s impossible.... but 10/10 AR malfunctions are operator/assembler induced.
Tried multiple mags??
is the gas block all the way to one side? (Ran out of adjustment)
where is the ejection 1-6 o’clock?
is the gas block on straight?
is it tight?
what are the other component?
who put it together?
what ammo. What cartridge?
Need some more info.
You're adjustable gas block needs to be opened up another notch... Stick a wrench in it, and open the port until it starts cycling correctly. Start with 1 notch, shoot one round, and see if it picks up the next. If not, open it up one more... Then repeat the process until it cycles properly and picks up the next round.
If you have a 6-position collapsable stock, you should be running a milspec CARBINE-length spring & buffer, and not a rifle-length spring and buffer. Those are only for A1 and A2 style buttstocks. If that still doesn't help, you might need to slow down your BCG and put an H2 buffer in it.
If you have a 6-position collapsable stock, you should be running a milspec CARBINE-length spring & buffer, and not a rifle-length spring and buffer. Those are only for A1 and A2 style buttstocks. If that still doesn't help, you might need to slow down your BCG and put an H2 buffer in it.
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Also make sure the gas block is seated directly over the port (in-line with the set-screw indents, and NOT seated directly up against the barrel shoulder. There needs to be a tiny gap if you are using a free-floating handguard, and are NOT using an older Delta ring style handguard.
- Nov 3, 2010
- 9,701
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I have a rifle length buffer a s buffer tube with an a2 stock so the spring is correct. The gas block is being run to allow the maximum amount of gas possible right now.
2 mags were used same result with both that’s all I had with me at the range.
ejection is between 3 and 4 ovlock
gas block appears to be installed correctly and is tight I will be checking the gas block later to make sure there are no alignment issues
I put this together and is far from my first time so although it’s not impossible the chances of an installation issue is not highly likely
I was firing federal xm193 range ammo
Adequate lubrication? Being new and not broken in, you'd want more not less.
It
It was lubed before the range trip so I don’t think that is the issue here. This is my first 18 inch rifle length barrel and I know some have had gas port sizing issues with them so that was my first thought
I used a feeler guage to set the distance from the shoulder to the gas block, it is a clamp on gas block so I didn’t dimple the barrel. I could swap out the spring but to my understanding the green spring is standard strength
Ah gotcha. Yeah I think I would start with the gas block. And what weight buffer are you using?
Close the GB completely and start opening it until it cycles and locks open with one round loaded in the magazine.
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This was done and even at full gas pressure it’s not picking up another round or locking back
I hear a lot of people have that problem...That's why so many women cheat...
Yeah, I'd get a dimpling tool. Rainier Arms sells some really nice ones. I'd also get a GB drilling/pinning tool to ensure it doesn't slip around if the set-screws come loose.
I'd say might be mis-sized gas port...Probably needs to be opened up. I'd contact the barrel manufacturer.
A bore scope would come in handy to check the alignment of the block to the gas port
Just cause you set the block gap with a feeler gauge does not mean your gas port is lined up correctly. With a superlative open all the way and lined up perfectly with the gas hole in the barrel it would more then likely cycle all the way dispite the buffer used. Gas hole in barrel is typically plenty large and the block open all the way is plenty of gas. Need to make sure those two holes are cleanly aligned and your problem will go away. IMO
You're not into bleed off territory on the AGB are you? I forget the exact number, but I think like 14 clicks is full open with no gas bleed off, so full gas pressure.
How does it cycle by hand, slowly? Feel any tight spots? When I break them in I dip the BCG in motor oil and blast a few mags through to really get everything running smooth. Then you can clean it off and get by with rem oil or whatever.
How does it cycle by hand, slowly? Feel any tight spots? When I break them in I dip the BCG in motor oil and blast a few mags through to really get everything running smooth. Then you can clean it off and get by with rem oil or whatever.
I shoul
I shouldn’t be, I will have to double check superlative arms instructions but I’m pretty sure 4.5 turns is maximum pressure beyond that and you start to bleed off gas. I think it’s 18 clicks. Rifle cycles by hand fine, the upper was cerekoted so it’s possible that’s slowing things down alittle as well until it’s fully broken in.
Does the BCG lock back?
Here's something to read,it will save you time.
Here's something to read,it will save you time.
AR15BARRELS.COM - Randall's description of AR gas operation and how everything works in harmony
How the AR-15 gas system works
ar15barrels.com
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While assembler error is usually the first suspect...it is never an absolute. I saw a post above that said it was 10/10 the builder's fault, and that is absolutely incorrect.
I put together a large frame AR last year that gave me fits. My nitride coated (will never do that again) CMC gas tube was completely obstructed. Swapped that out and was short stroking still on a completely open and aligned gas block...went through everything. Finally checked the gas port on my Criterion barrel... .068" for a rifle length gassed, 18" .308. Opened it up to .093", and it's never missed a beat since. I had that upper fully apart three times. Burn rings around the ports were perfect...Swapped two buffers and springs...what a damn headache. I probably could have got away with just .020" increase, but an adjustable block is easier to screw with than drilling out a barrel a second time. By that point I was done with screwing around.
I'm not saying that this is the reason the OP is having issues, it can be one of many things. However if EVERYTHING is properly aligned/installed, and you haven't checked the gas port size on your barrel its time to do so. If your gas tube is coated like it doesn't need to be, you might want to check flow through it too.
I put together a large frame AR last year that gave me fits. My nitride coated (will never do that again) CMC gas tube was completely obstructed. Swapped that out and was short stroking still on a completely open and aligned gas block...went through everything. Finally checked the gas port on my Criterion barrel... .068" for a rifle length gassed, 18" .308. Opened it up to .093", and it's never missed a beat since. I had that upper fully apart three times. Burn rings around the ports were perfect...Swapped two buffers and springs...what a damn headache. I probably could have got away with just .020" increase, but an adjustable block is easier to screw with than drilling out a barrel a second time. By that point I was done with screwing around.
I'm not saying that this is the reason the OP is having issues, it can be one of many things. However if EVERYTHING is properly aligned/installed, and you haven't checked the gas port size on your barrel its time to do so. If your gas tube is coated like it doesn't need to be, you might want to check flow through it too.
Does the complete BCG work fine in a different upper? Is the gas key loose? Is there a verified pathway through the gas key into the carrier? Is the gas tube installed correctly and not upside down?
I did not see these easy culprits in the above discussion.
A loose/occluded gas key will present itself with some random problems.
I did not see these easy culprits in the above discussion.
A loose/occluded gas key will present itself with some random problems.
Everything was properly installed, I tore it all apart and put it back together again, going back to the range tomorrow to see if I can get it running. If not I need to get some pin gauges and measure the gas port
I'm gonna throw this out there, because it puzzled me. Please allow me to offer a recent observation at the range.
New buddy I met at the range said lets go shooting, so off we go. He has a 6.5 Grendel AR, and shot two different boxes of store-bought ammo. I dont know jack about 6.5, Grendel, and barely jack about ARs. But this is what happened:
One variety of store bought ammo fired perfectly and cycled the rifle just fine, ejecting 4 or 5 feet at 2 o clock.
The other ammo fired, but the rifle didnt pick up the next round and he had to hand cycle. Ejection for these rounds was about one foot at 4 or 5 o clock position.
"Those first rounds are hotter," I observed, "these others wont cycle fully." hmmm, need more lube? Nah, plenty he says.
He texted me next day from the range, saying his fix for the problem was to drill a hole in the buffer tube, and lube the buffer spring. I said what? He drilled a big hole in his buffer tube, supposedly allowing AIR PRESSURE to bleed off, because his opinion was that the buffer was acting like an air piston somehow had enough seal to hinder the cycling. I said I never heard anything like that before, but he says the lower pressure ammo now works great and problem solved... (I just shrug my shoulders and call him a jarhead.) Your thoughts?
Is this even possible? For an AR buffer tube to be so airtight it actually compresses air & hinders cycling?
New buddy I met at the range said lets go shooting, so off we go. He has a 6.5 Grendel AR, and shot two different boxes of store-bought ammo. I dont know jack about 6.5, Grendel, and barely jack about ARs. But this is what happened:
One variety of store bought ammo fired perfectly and cycled the rifle just fine, ejecting 4 or 5 feet at 2 o clock.
The other ammo fired, but the rifle didnt pick up the next round and he had to hand cycle. Ejection for these rounds was about one foot at 4 or 5 o clock position.
"Those first rounds are hotter," I observed, "these others wont cycle fully." hmmm, need more lube? Nah, plenty he says.
He texted me next day from the range, saying his fix for the problem was to drill a hole in the buffer tube, and lube the buffer spring. I said what? He drilled a big hole in his buffer tube, supposedly allowing AIR PRESSURE to bleed off, because his opinion was that the buffer was acting like an air piston somehow had enough seal to hinder the cycling. I said I never heard anything like that before, but he says the lower pressure ammo now works great and problem solved... (I just shrug my shoulders and call him a jarhead.) Your thoughts?
Is this even possible? For an AR buffer tube to be so airtight it actually compresses air & hinders cycling?
Yes and yes. most mil spec buffer tubes have a hole drilled in the end to let out moisture and allow air to escape. Even the stock screw for an A2 stock has a hole drilled down the center. If you oil your buffer tube spring and shoot you will have a nice oil stain on your shirt from oil being pushed out that hole.
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I don’t remember seeing the answer to this, have you tried another BCG? Was a the range a while back and one of the officers was having weird intermittent cycling issues. Primer made its way into the gas key. New BCG and no more issues.
Same result with two different BCG’s and after reassembly of the gas block to the barrel. Now I’m in the process of ordering pin gauges to check gas port size
After reading the entire thread I first second the idea of using a borescope to check gas block alignment and to adjust the AGB wide open as a starting point. Put enough AR's together and you'll have enough of these specific is issues causes by defective sized blocks, hairline cracks in blocks, etc, etc.. where it's just something you check every time. 2m during assembly on the bench can save hours of head scratching on the range.
Next I'd try another BCG and all BCG related components including running a borescope of your buffer tube. I've gotten A LOT of really poorly machined buffer tubes and if there are ridges on the interior it can slow down your system.
And then ammo. Wouldn't be the first or hundredth both of XM193 that wasn't right.
Good luck.
The pin gauges won't help you much at this point. What are you going to do with the information? As long as there is a port hole in the barrel close to the appropriate size you should be tuning things to function with that adj gas block. Almost every suggestions by folks here seems to have been tried or n/a to your issue,
Save the $ on gauges and send the upper to a gunsmith.
Not as knowledgeable but had a similar sounding problem with an old SKS I bought. Tried cleaning the gas tube, fiddling with the grenade launcher attachment that was completely foreign to me, nothing worked. Gave up and took it to my smith who was way behind on orders.
About 6 weeks later he called and said it was ready........turned out to be the magazines were hanging the rounds........he filed down the three mags I had, and happy days are here again! Hope your problem might be similarly easy!
Only if you’re using a stock that exposes the end of the buffer tube. I put a light coat of lube on my spring and obviously storing rifles muzzle up in the safe, gravity pulls any excess down there. No issues with oil covered shirts. If it’s a concern, take a 7.62cal bore patch and put it in the bottom of the tube to soak up any oil and put the spring in. The cotton will allow air to escape while still soaking up any lubricants.
Recently assembled a 6ARC using a barrel from a highly respected source and brand. Was having the same issue and it was definitely under gassed (24” rifle +2” from the manufacturer with a .080” port. Another member here with a barrel from the same place was having the exact same issue around the same time) Opened the port up to .093” and it runs like a champ now.
Being able to pin the gas port would possibly give him some info...whether or not it’s a potential source of the problem. Could’ve been incorrectly sized at the factory, but if it’s “in range” then the info isn’t the end all be all answer but it’s more information that can be used to pin point it
But you are right, sending it to a smith who can diagnose it and already has the tools to do so, as well as the tools to remedy it can save a lot of headaches
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They are going to determine if the port is undersized and the manufacturer should make this right on their dollar or if I need to pay a gunsmith to do work on the rifle.
Dropping a rifle off at a gunsmith, paying him to look for a potential manufacturer defect and then waiting weeks for an answer from him is not as appealing as doing alittle bit of leg work my self.
Having any firearm that doesn’t work is not appealing! If you don’t have the knowledge And are relying on the hide for the answer then it may be worth having it done correctly. You may have the knowledge idk, I’m not calling you out just saying sometimes it’s best to get a professional to cure the issue for something you may need to save your life one day.
If the gun won’t run with gas block fully open my suggestion is try the lightest buffer/spring combo and get a lighter carrier. Try a AR 15 carrier first then get a lightweight carrier if that doesn’t work. You can always close the gas block more to accommodate the new parts.
If that doesn’t work then you have other issues
Possibly try other mags (I know you mentioned trying 2 but make sure you try another brand)
What does the rifle feel like? I had a mag issue a couple weeks ago. A gun that runs flawlessly all the sudden won’t lock back on the empty mag. I cleaned the rifle, same result. Then turned my bootleg carrier wide open. Same issue but noticeable recoil beating the gun up.
Turned out to be the mag. But was confused for a bit. Every other mag runs flawlessly with prior setting. Magpul pmags
If that doesn’t work then you have other issues
Possibly try other mags (I know you mentioned trying 2 but make sure you try another brand)
What does the rifle feel like? I had a mag issue a couple weeks ago. A gun that runs flawlessly all the sudden won’t lock back on the empty mag. I cleaned the rifle, same result. Then turned my bootleg carrier wide open. Same issue but noticeable recoil beating the gun up.
Turned out to be the mag. But was confused for a bit. Every other mag runs flawlessly with prior setting. Magpul pmags
A set of pin gauges would be nice to have. But a good set of number drill bits will do the same. And you always need drill bits!
Any chance the gas tube is rubbing against the inside of the carrier key?
Does the bcg drop right into place with upper off and muzzle pointed to the floor? Or is there resistance?
Does the bcg drop right into place with upper off and muzzle pointed to the floor? Or is there resistance?
A simple question, similar to a Helpdesk tech asking if the computer is plugged in - do you have a rifle-length buttstock, buffer and buffer tube? Not advised to mix rifle length barrel & gas tube with carbine length buttstock. Not that you're doing this, of course, but worth mentioning none the less.
How does it feel when you shoot it? Can you feel the carrier changing directions? Anytime I’ve had a rifle under gassed I can easily feel how slow the carrier is moving. The bounce of it changing directions and then slowly closing is a distinct feel.
