View Full Version : 1:00 ejection & Short stroking ?
My 16" mid length with 4oz T2 buffer is throwing brass lazily at 1:30 but short stroked 3 times in 150 round range session. I never had a feeding issue until yesterday. The brass was ejecting only 3 feet away and slowly but at a 1 to 2 o'clock pattern. I was thinking replace T2 with standard buffer but the ejection pattern suggest I need heavier buffer. How can over gas signs & under gased signs happen at same time, I'm confused. I was shooting IMI 55 grain .
Any help is appreciated.
Those much more knowledgeable then I should be chiming in pretty quick - in the mean time ejection pattern is not the last word on the status of your gas system. It sounds like extractor/extractor spring problem.
Thanks. You think the extractor force could be too heavy, I got a standard 4 coil with rubber insert, plus O-ring. I'll remove O-ring
Something I'll try out. I'll also throw in a standard carbine buffer.
Thanks. You think the extractor force could be too heavy, I got a standard 4 coil with rubber insert, plus O-ring. I'll remove O-ring
Something I'll try out. I'll also throw in a standard carbine buffer.
The short stroking probably has nothing to do with the extractor, I would leave the o-ring on the extractor spring. Your buffer weight is probably too heavy, or your recoil spring might be too strong (unless it’s a standard recoil spring). I would swap out the H2 buffer with a H buffer, and if that doesn’t work then a normal carbine buffer. Keeping good strong extraction tension is a positive in my book. Try the different buffers first & report back & tell us what happens. Good luck.
Thanks. I'll run it with a couple different buffer weights.
A forward ejection with sufficient extractor tension will not be caused by too much buffer weight. What barrel are you using?
You are almost certainly not experiencing short stroking, but much more likely an extremely overgassed rifle.
Thanks. You think the extractor force could be too heavy, I got a standard 4 coil with rubber insert, plus O-ring. I'll remove O-ring
Something I'll try out. I'll also throw in a standard carbine buffer.
Yeah, I actually was not thinking / saying the extractor force was "too heavy"
I was thinking (based on your description) the cartridge case MIGHT be leaving the bolt face prematurely.
Anyway, - far more helpful than my "thoughts" - somewhere around the forum here is a trouble-shooting flow-chart that can help you approach this in a logical manner. Random swapping/tweaking/removing/replacing, without Variable Isolation, is a good recipe for lots of wasted time and ammo before you learn the actual culprit / culprits
Good luck, and keep us posted.
A forward ejection with sufficient extractor tension will not be caused by too much buffer weight. What barrel are you using?
You are almost certainly not experiencing short stroking, but much more likely an extremely overgassed rifle.
This would be my thought as well. My 13” mid barrel with 0.076 gas port has a violent bolt speed with a regular carbine spring and buffer.
Issues I thought were short strokes were from excessive bolt speed.
After moving to A5 lower with a5h2 buffer it’s the smoothest shooting rifle I own.
Sent from my iPhone using Tapatalk
Two things to start with:
1. Get rid of the stupid O ring. There's no need for it on any decent gun. AND,
2. Look at the gas key end of the Gas tube. If it looks worn smooth and doesn't have that "bulb" shape, you need to replace the tube.
That IMI ammo could be the problem too of course. But I've had to replace 2 middy gas tubes in the past because they wore down prematurely and leaked so much gas, the guns' reliability suffered.
2. Look at the gas key end of the Gas tube. If it looks worn smooth and doesn't have that "bulb" shape, you need to replace the tube.
In your experience what causes the premature wear of the bulb on the end of the gas tube?”
In your experience what causes the premature wear of the bulb on the end of the gas tube?”
Not @markm, but the answer to your question is slight misalignment between the gas key and tube. I've had to replace a tube on a mid length before and it turns out the gas block had come loose. Ultimately, I imagine with enough rounds even a perfectly aligned gas tube will wear down.
If your problem just started recently and there was no problems with the buffer weight before
I would for sure check for gas leaks before changing buffer weight I shoot a lot of IMI 55 gn. ammo
and it is a hot load and has 27.5 gn. of powder in it
That is where I would start.
In your experience what causes the premature wear of the bulb on the end of the gas tube?”
There HAD TO have been a batch of shitty tubes. In middy specifically. There was another guy here who had similar experiences. I first thought the gas key had roughness inside and was wearing out the tube, but that wasn't it.
I use one of these. Mine are all good so far.......However, it it weren't a thing, this wouldn't exist.
Gas Tube Gauge (https://www.brownells.com/gunsmith-tools-supplies/rifle-tools/gas-system-tools/ar-15-m16-gas-tube-gauge-prod41043.aspx)
Both of my tubes failed on relatively low round counts. I don't know if these tubes didn't get some sort of proper heat treatment or something, but they were worn down to the regular diameter of the tube and puking fouling under the handguard.
This would be my thought as well. My 13” mid barrel with 0.076 gas port has a violent bolt speed with a regular carbine spring and buffer.
Issues I thought were short strokes were from excessive bolt speed.
After moving to A5 lower with a5h2 buffer it’s the smoothest shooting rifle I own.
Sent from my iPhone using Tapatalk
I tried a standard 3 oz buffer & it started ejecting at 3 o'clock but still only about3 feet. I recorded it in slow motion & it's bouncing the brass off the brass deflector but still lazy ejection.
My main concern is it's not 100 % reliable with GI aluminum mags. I get 2 to 3 short stroke stoppages (round is under bolt half way) per mag.
I'm using D&H & Okay mags. PMags seem GTG.
It's a 16 inch factory Spikes ST15.
I think it's under gased. The new round is stuck under the bolt, as if the bolt didn't go back far enough to pick up next round, but the bolt locks back on empty mag every time. I can't figure it out.
Thanks for the help.
Inkslinger
04-04-22, 16:44
How old are the springs in the mags causing problems? I imagine if it’s overgassed (which being Spikes it probably is) and you have magazine springs that are worn out, you could end up with what you just described. It’s not the bolt going back far enough, it’s the magazine springs not having enough force to get the round up quick enough for the bolt to pick it up.
If your problem just started recently and there was no problems with the buffer weight before
I would for sure check for gas leaks before changing buffer weight I shoot a lot of IMI 55 gn. ammo
and it is a hot load and has 27.5 gn. of powder in it
That is where I would start.
It's only with GI mags, I can't remember if I only ran P mags in it & no aluminum mags, because I do like mixing GI & P mags for training. It runs 100 percent with P mags but still a weak ejection. I'm getting 3 stoppages per GI ma, the Bolt over the new round like a short stroke, but bolt locks open.
I never noticed it beforehand. Like I said it was ejecting 1:30 with a 4 oz buffer now 3:00 with a 3 oz buffer so that is strange.
But I'm thinking of opening the gas port, via drill bit lol. I'm thinking about it. It's that frustrating. It's a factory gun, I never had a stoppage with a "home build" I been lucky I guess. The gun was my son's he wanted to sell it I bought it
I think it's under gased.
It sounds like it, but under gassing would be almost unheard of with most guns being over gassed. Any signs of leakage around the gas block or gas key?
Any other ammo you can try?
Both of my tubes failed on relatively low round counts. I don't know if these tubes didn't get some sort of proper heat treatment or something, but they were worn down to the regular diameter of the tube and puking fouling under the handguard.
I don't see any signs of leaking gas. I even put paper around gas tube where it goes into gas block, the paper doesn't move or get tore up. The Carrier & upper are clean looking, I ran another carrier & ran that carrier in other gun. I pulled my gas block (pinned from factory)had perfect alignment. I'm thinking about opening the gas port, since I got it apart. Crazy, but It's not reliable, I value reliability over everything. What's your thoughts on opening gas port a hair. My son has pinned front sights & gas blocks so I got some knowledge to help me.
Inkslinger
04-04-22, 17:12
I don't see any signs of leaking gas. I even put paper around gas tube where it goes into gas block, the paper doesn't move or get tore up. The Carrier & upper are clean looking, I ran another carrier & ran that carrier in other gun. I pulled my gas block (pinned from factory)had perfect alignment. I'm thinking about opening the gas port, since I got it apart. Crazy, but It's not reliable, I value reliability over everything. What's your thoughts on opening gas port a hair. My son has pinned front sights & gas blocks so I got some knowledge to help me.
Take it to someone who has pin gages before you start drilling things. Like I said above, I would try new springs in the problem mags before you start removing metal.
Yeah, I would definitely measure the gas port size before doing any drilling.
You can’t really do that over.
Agree on reaming the port being the LAST option. If the Port is .076" or greater, that isn't the problem.
I have this large needle that I mark with a sharpie. I poke it into the port, and use calipers to measure where it stops inside the port. Not perfect, but it gets me within 1 or 2 thousandths which is good enough.
It sounds like it, but under gassing would be almost unheard of with most guns being over gassed. Any signs of leakage around the gas block or gas key?
Any other ammo you can try?
The gas port was .063..... I opened it up. I won't say how much because that will be a can of worms, but let me say .080 is not large as .093 is common even on mid length gas systems. The spent brass was falling out 3 feet, I think the bolt was hitting the cases as it was closing shooting them forward at 1:30 but with a lighter buffer I got them to 3:00 still only about 3 feet with intermittent stoppages.
I opened it up a bit & but still not much change. Now going wide open. I'll post tomorrow when I give it a go. Thanks for the help.
Take it to someone who has pin gages before you start drilling things. Like I said above, I would try new springs in the problem mags before you start removing metal.
The mags are newer like 150 to 300 rounds through them & have run in 3 other longer & shorter AR's. IDK it's now a obsession to get it to run reliable, & a father & son quest, lol. My son is ready to drill. I'm letting him it's only a barrel.
Thanks for the help.
This might be a Dum question, but have you checked the tension on the ejector spring
taken it apart and cleaned the spring and ejector and lube them?
The gas port was .063..... I opened it up. I won't say how much because that will be a can of worms, but let me say .080 is not large as .093 is common even on mid length gas systems.
Wow. .063" on a 16" middy??? That's lean. For me .076" one a 14.5" middy is a touch lean to where I drop the buffer weight down to H buffer from H2, and it's perfect.
I have a .080" 14.5" middy that's gassed where you'd probably really want it for adverse conditions reliability.
Wow. .063" on a 16" middy??? That's lean. For me .076" one a 14.5" middy is a touch lean to where I drop the buffer weight down to H buffer from H2, and it's perfect.
I have a .080" 14.5" middy that's gassed where you'd probably really want it for adverse conditions reliability.
I opened the gas port to .075 no improvement so I finally opened to .093 now it's ejecting just a bit further now about 5 feet & closer to 3:00 with the T2 buffer back in. I'm gonna run a few mags before I declare it stopped the "short stroking" for sure, but it's not running sluggish anymore. I wasn't gonna say how much I opened it up to because of all the flack larger gas port sizes get, but figured someone else could benefit from my information. I opened the port as a last resort after many rounds of testing & trying different less permanent solutions, it worked for me & my wants & needs; to make my particular AR reliable.
I am buy no means recommending this is a solution for every AR or everyone. Thanks again to everyone, I appreciated the help & suggestions.
If any trouble comes up I'll let you all know.
That's interesting. Based on my middys/ports that sounds massive, but if it works, that's good. Update us if you get some more time on the gun.
I got a new barrel in today.
416R Stainless - Wilson Combat - 16" - 556 Nato - 1/8 - Midlength. It measured at exactly .078 as in my experience, it falls into the .076/78 range as most of my other 16" midlength 556 barrels.
.063 is indeed on the lean side, but .093 sounds Yuge and I suspect there may be more than one issue if you had to open it up that much.
Is there a barrel length / gas length / optimum gas port size chart anywhere?
https://uploads.tapatalk-cdn.com/20220405/d1b360963484334c52ca65b4b5dcad0f.jpg
ETA: I looked a bit and found these, not sure if 100% accurate. I was able to find Colt uses .063 for a 16" Carbine length gas system so yours may have been a mistake.
GAS PORT SIZES (https://www.tacticalmachining.com/learn/ar-style-rifles/ar-15-gas-port-sizes.html)
.063 is indeed on the lean side, but .093 sounds Yuge and I suspect there may be more than one issue if you had to open it up that much.
That's my though too. But I've also seen some majorly Effed up ammo come from Israel... I mean scary bad ammo.
One More Time
04-05-22, 18:32
I got a new barrel in today.
416R Stainless - Wilson Combat - 16" - 556 Nato - 1/8 - Midlength. It measured at exactly .078 as in my experience, it falls into the .076/78 range as most of my other 16" midlength 556 barrels.
.063 is indeed on the lean side, but .093 sounds Yuge and I suspect there may be more than one issue if you had to open it up that much.
Is there a barrel length / gas length / optimum gas port size chart anywhere?
I have read posts from Clint of BRT say that 0.078" is the largest he likes to see on a 16" middy.
His barrels are sized to run an A5H0 or H1 buffer.
MY Faxon 16" mid gas has an .081" gas port and with that I was getting lock back with an A5H4 buffer and Tubbs flat wire spring.
The BRT tube I got sized for an A5H2 buffer is .076", equivalent to a .073" gas port if I read the sizing note correctly.
This chart has a few different barrel length, gas system length gas port sizes.
https://docs.google.com/spreadsheets/d/1tXunBDX5Gaz87BqxwNxDUlWNK9nEv-cZEQoLq2JXXrk/htmlview
The FN 14.5" mid gas I just got should have a .076" port, which should run well with an A5H2 buffer.
My Wilson barrel is off getting finished before shipping and I have been itching to know what the gas port is.
Looks like it should be .078", should run fine with the A5H2 I have.
I don't have anything shorter than 14.5" so run the A5 action and mid gas on everything.
An efficient gas system needs less gas to be reliable.
My Wilson barrel is off getting finished before shipping and I have been itching to know what the gas port is.
Looks like it should be .078", should run fine with the A5H2 I have.
I don't have anything shorter than 14.5" so run the A5 action and mid gas on everything.
An efficient gas system needs less gas to be reliable.
Good information, that is exactly what I have for the barrel pictured above.
I would def try another brand of ammo, good ammo. Usually the IMI is hot as fck so it makes no sense but still. Try different variables. As far as buffers go, I am a tried and true believer in the A5 buffer systems. Very nice but not necessary.
It sux when your shit doesn't run.
PB
One More Time
04-05-22, 19:18
Good information, that is exactly what I have for the barrel pictured above.
I don't know where my head is at, long day and mid gas on the brain I guess.
I'm waiting on an 18" rifle gas barrel, not a mid gas.
First one with this barrel length and rifle gas for me.
Still using the A5H2 on it.
I would def try another brand of ammo, good ammo. Usually the IMI is hot as fck so it makes no sense but still. Try different variables. As far as buffers go, I am a tried and true believer in the A5 buffer systems. Very nice but not necessary.
It sux when your shit doesn't run.
PB
I also ran Lake city 62 grain too, while trying to figure out the lazy ejection & short stroke type ftf.
A mid length 18 inch is a .093 gas port from most makers. It was not a reliable gun so I would rather take the chance I did & it paid off so far
I couldn't have sold my upper/ barrel that wasn't reliable with good conscience to anyone. So, I operated on it. I can say I've did that & it works.
I could have went in-between .080 & .093, but It was sluggish, now I know it's gassed & I could put a adjustable gas block but don't want or need to. Every barrel has its own personality, slow, fast, accurate, clean running, mine was stingy with the gas. It was a soft shooting gun, still is. It's just a bit more reliable..... I'll know for sure after a few more rounds through it.
I don't know where my head is at, long day and mid gas on the brain I guess.
I'm waiting on an 18" rifle gas barrel, not a mid gas.
First one with this barrel length and rifle gas for me.
Still using the A5H2 on it.
Your 18" rifle gas barrel has a .078" gas port? Rainier claims mine has a .089" port and its certainly not overgassed by any stretch of the imagination. I am using an A5H2, FWIW.
Andy
I have one of the Rainier 18 rifle gas barrels, A1 Magpul stock, runs like a champ, super smooth.
Your 18" rifle gas barrel has a .078" gas port? Rainier claims mine has a .089" port and its certainly not overgassed by any stretch of the imagination. I am using an A5H2, FWIW.
Andy
He doesn’t have it yet, so doubt that is what he was saying.
Is there a barrel length / gas length / optimum gas port size chart anywhere?
This is what I've collected from various sources:
SOLGW GAS PORTS:
10.5" Carbine .073
11.5" Carbine .071
12.5" Carbine .068
14.5" Carbine .0625
16" Carbine .0625
13.7" Mid .0785
14.5” Mid .077
16" Mid .076
18" Rifle .0995
20" Rifle .093
Textbook TDP GAS PORTS:
Mk18 10.3” Carbine .070
M4 14.5" Carbine .0625
Mk12 18” Rifle .0995
M16 20" Rifle .093
CRANE 14.5 Mid-Length gas port reportedly .076
AR15 Gas Port Sizes
Disclaimer: These are lists of compiled information from multiple sources. While we make our best effort to test and produce these should be considered for reference only. Any time you start messing with the gas port on your rifle you run the risk of destroying the barrel or causing it to be over gassed. It is much better to slowly work your way up to what you would be happy with.
AR-15 Platform 5.56mm
20" rifle 5.56 0.0935
20" rifle 5.56 0.096
20" rifle 5.56 0.098
16" mid 5.56 0.078
16" mid 5.56 0.081
16" car 5.56 0.0625
16" car 5.56 0.065
16" car 5.56 0.07
14.5" car 5.56 0.067
14.5" car 5.56 0.086
11.5" car 5.56 0.081
11.5" car 5.56 0.089
24" rifle 5.56 0.089
And this seems to go with the chart you posted:
The USGI M4 is not 0.070-0.086". The port diameter as spec'd by Colt is 0.0625"/0.063", or 1/16th of an inch.. This is so because of the USGI M16 is listed as 0.092"/0.093" or 3/32nd of an inch. How is this so? Due to port pressure of a M16 is 13,000psi while the M4 ramps up to 26,000psi. If your still boggled, this is the fact that the dwell time factors off a distance of 7 inches from port to muzzle.
Gas passes through a 0.092-inch-diameter port in the barrel, located 13.2 inches forward of the bolt face (with the bolt in the locked position)
The carbine gas port is located closer to the chamber than the gas port of the rifle: 7.5 inches instead of the 13 inch distance on the rifle. The gas pulse therefore enters the gas tube sooner and reaches the carrier group earlier than it does in the rifle length barrel. In addition to reaching the carrier sooner, it reaches it at higher pressure. The gas pressure at the carbine’s gas port is double that of the rifle: 26,000 psi vs. 13,000 pounds per square inch. (ArmaLite)
It is necessary to remember that the 5.56×45 NATO cartridge was designed specifically for a 20-inch barrel on a gas operated weapon with 7 inches of dwell time after the gas port. The 14.5-inch M4 barrel retains the 7 inch dwell length after the gas port.
Armalite Technical Note #48: The carbine gas port is located closer to the chamber than the gas port of the rifle: 7.5 inches instead of the 13 inch distance on the rifle. The gas pulse therefore enters the gas tube sooner and reaches the carrier group earlier than it does in the rifle length barrel. In addition to reaching the carrier sooner, it reaches it at higher pressure. The gas pressure at the carbine’s gas port is double that of the rifle: 26,000 psi vs. 13,000 pounds per square inch.
COLT GAS PORT DIAMETER: (reportedly this is from Colt reference material)
67741
Another reference for gas port sizes which is updated: https://docs.google.com/spreadsheets/d/1tXunBDX5Gaz87BqxwNxDUlWNK9nEv-cZEQoLq2JXXrk/edit#gid=766121382
This is what I've collected from various sources:
SOLGW GAS PORTS:
10.5" Carbine .073
11.5" Carbine .071
12.5" Carbine .068
14.5" Carbine .0625
16" Carbine .0625
13.7" Mid .0785
14.5” Mid .077
16" Mid .076
18" Rifle .0995
20" Rifle .093
Textbook TDP GAS PORTS:
Mk18 10.3” Carbine .070
M4 14.5" Carbine .0625
Mk12 18” Rifle .0995
M16 20" Rifle .093
CRANE 14.5 Mid-Length gas port reportedly .076
AR15 Gas Port Sizes
Disclaimer: These are lists of compiled information from multiple sources. While we make our best effort to test and produce these should be considered for reference only. Any time you start messing with the gas port on your rifle you run the risk of destroying the barrel or causing it to be over gassed. It is much better to slowly work your way up to what you would be happy with.
AR-15 Platform 5.56mm
20"rifle5.56 0.0935
20"rifle5.56 0.096
20"rifle5.56 0.098
16"mid5.56 0.078
16"mid5.56 0.081
16"car5.56 0.0625
16"car5.56 0.065
16"car5.56 0.07
14.5"car5.56 0.067
14.5"car5.56 0.086
11.5"car5.56 0.081
11.5"car5.56 0.089
24" rifle5.56 0.089
And this seems to go with the chart you posted:
The USGI M4 is not 0.070-0.086". The port diameter as spec'd by Colt is 0.0625"/0.063", or 1/16th of an inch.. This is so because of the USGI M16 is listed as 0.092"/0.093" or 3/32nd of an inch. How is this so? Due to port pressure of a M16 is 13,000psi while the M4 ramps up to 26,000psi. If your still boggled, this is the fact that the dwell time factors off a distance of 7 inches from port to muzzle.
Gas passes through a 0.092-inch-diameter port in the barrel, located 13.2 inches forward of the bolt face (with the bolt in the locked position)
The carbine gas port is located closer to the chamber than the gas port of the rifle: 7.5 inches instead of the 13 inch distance on the rifle. The gas pulse therefore enters the gas tube sooner and reaches the carrier group earlier than it does in the rifle length barrel. In addition to reaching the carrier sooner, it reaches it at higher pressure. The gas pressure at the carbine’s gas port is double that of the rifle: 26,000 psi vs. 13,000 pounds per square inch. (ArmaLite)
It is necessary to remember that the 5.56×45 NATO cartridge was designed specifically for a 20-inch barrel on a gas operated weapon with 7 inches of dwell time after the gas port. The 14.5-inch M4 barrel retains the 7 inch dwell length after the gas port.
Armalite Technical Note #48: The carbine gas port is located closer to the chamber than the gas port of the rifle: 7.5 inches instead of the 13 inch distance on the rifle. The gas pulse therefore enters the gas tube sooner and reaches the carrier group earlier than it does in the rifle length barrel. In addition to reaching the carrier sooner, it reaches it at higher pressure. The gas pressure at the carbine’s gas port is double that of the rifle: 26,000 psi vs. 13,000 pounds per square inch.
COLT GAS PORT DIAMETER: (reportedly this is from Colt reference material)
67741
Another reference for gas port sizes which is updated: https://docs.google.com/spreadsheets/d/1tXunBDX5Gaz87BqxwNxDUlWNK9nEv-cZEQoLq2JXXrk/edit#gid=766121382
Fantastic information. Thank-you.
What the heck is that "AR-15 platform 5.56mm" ports?
Just the sight of those 11.5 ports over .080" is pissing me off.
Ran it after opening up gas port, no short stroke ftf, had 1 stove pipe out of 4 mags. I Never had a stove pipe before. Ejection was sharper but not to aggressive around 2:30 to 3:00 still around 4 ft maybe 5 ft. It ejected a few rounds to 4:30 - 5:00 IDK ?, so I also remove O-ring, & ejection stayed at 2:30 3:00 & 4 to 5 feet, no stoppages.
Seems more reliable now. I recorded the ejection before opening gas port up, it was dribbling out of ejection port with a 3 oz buffer & .063 port. Plus could barely throw brass clear bolt was hitting brass as bolt closed.
I didn't want to open it to .093 but a 18 midlenth is .093.
I opened it to.080 first & I wasn't happy.
This is 1 incident with 1 AR, YMMV. Reliability was my goal, it's more reliable now.
I also checked for gas leaks & tried lighter buffers, mags, ammo, different buffer spring, before opening it up.
Only done as last resort.
Yeah, I actually was not thinking / saying the extractor force was "too heavy"
I was thinking (based on your description) the cartridge case MIGHT be leaving the bolt face prematurely.
Anyway, - far more helpful than my "thoughts" - somewhere around the forum here is a trouble-shooting flow-chart that can help you approach this in a logical manner. Random swapping/tweaking/removing/replacing, without Variable Isolation, is a good recipe for lots of wasted time and ammo before you learn the actual culprit / culprits
Good luck, and keep us posted.
With the price of ammo, figuring out what is the cause of malfunctions can quickly out price the cost of a new barrel. After looking into usual suspects, & trying various things. I opened up my port from .063, what seems way too tight on a midlenth 16. I opened up my gas port & stopped FTF & my ejection pattern went from 1:00 1:30 ish to 2:30 3:00 ish, & throwing brass 5'. It worked for me. This is a one off, just what I experienced.
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