"Over Gassed" AR's Fact or Fiction? Other Perspectives

I see a lot of postings suggesting AR failure to feed malfunctions may be because their rifle is "Over Gassed" and I really have to question this. For backdrop, I have built up and test fired in excess of 500 AR-15's, many of them with custom or wildcat cartridges, and with a myriad of barrel lengths, gas system lengths, etc., where there was no recognized or normally accepted port sizing (had to figure it out).

One of the main arguments of the failure to feed malfunction as relates to "Over Gassing" is that the bolt carrier and bolt speed is too fast.

I have yet to see "Over Gassing" as a source of a failure to feed malfunction to be a real issue for a few reasons:

1. The speed of the carrier and bolt coming forward to feed a round is almost 100% governed by the stiffness of the buffer spring and the weight of the buffer.
2. If a rifle is "Over Gassed", that may speed up the retreat of the carrier and the unlocking of the bolt out of battery, but it does not per se speed up the carrier and bolt coming forward (i.e. the buffer typically hits the back of the buffer tube and the dead plastic end of the buffer softens that strike so it's not metal to metal, but it's not a trampoline effect, nor was an AR buffer system designed to do that).
3. An AR gas system is set up to bleed off all gas immediately after the bolt opens out of battery (i.e. it blows out the vent holes in the side of the carrier) so it's not like the system holds onto excess pressure to somehow convert that into carrier or bolt speed coming forward.

I am also not a big fan of adjustable gas blocks and I have seen plenty of issues with them (taken a bunch of them off customer guns a returned them because they were a source of a problem that did no exist). First off, an adjustable gas block is of no value at all unless the rifle is over ported. All an adjustable gas block can do is cut back the amount of gas being delivered into the gas system from the port, it can never add more than can come through the port. It may have some value for someone that wants to run something like a 300 BO where they want to shoot subsonic "heavies" with a real fast powder through a can to run very quiet (ergo they have a very large port to do that), but then wants to shoot supersonic and push bullets to the max where chamber pressures are running double what they are with a subsonic loading. Even then, what I typically see is an AR cycling back hard and ejecting aggressively but that's about it.

I have probably "opened a can of worms" here with this discussion but there are other perspectives on the issue involved.
 
i built a 556 that was jamming empty cases up, while it also tried picking up new round on the way forward.

The bcg speed was simply too fast for the case to clear the port. Reduced the gas a LOT and it worked like a dream.

Maybe my ejector was weakish?

Not questioning your experience, but it happens.
 
I see a lot of postings suggesting AR failure to feed malfunctions may be because their rifle is "Over Gassed" and I really have to question this. For backdrop, I have built up and test fired in excess of 500 AR-15's, many of them with custom or wildcat cartridges, and with a myriad of barrel lengths, gas system lengths, etc., where there was no recognized or normally accepted port sizing (had to figure it out).

One of the main arguments of the failure to feed malfunction as relates to "Over Gassing" is that the bolt carrier and bolt speed is too fast.

I have yet to see "Over Gassing" as a source of a failure to feed malfunction to be a real issue for a few reasons:

1. The speed of the carrier and bolt coming forward to feed a round is almost 100% governed by the stiffness of the buffer spring and the weight of the buffer.
2. If a rifle is "Over Gassed", that may speed up the retreat of the carrier and the unlocking of the bolt out of battery, but it does not per se speed up the carrier and bolt coming forward (i.e. the buffer typically hits the back of the buffer tube and the dead plastic end of the buffer softens that strike so it's not metal to metal, but it's not a trampoline effect, nor was an AR buffer system designed to do that).
3. An AR gas system is set up to bleed off all gas immediately after the bolt opens out of battery (i.e. it blows out the vent holes in the side of the carrier) so it's not like the system holds onto excess pressure to somehow convert that into carrier or bolt speed coming forward.

I am also not a big fan of adjustable gas blocks and I have seen plenty of issues with them (taken a bunch of them off customer guns a returned them because they were a source of a problem that did no exist). First off, an adjustable gas block is of no value at all unless the rifle is over ported. All an adjustable gas block can do is cut back the amount of gas being delivered into the gas system from the port, it can never add more than can come through the port. It may have some value for someone that wants to run something like a 300 BO where they want to shoot subsonic "heavies" with a real fast powder through a can to run very quiet (ergo they have a very large port to do that), but then wants to shoot supersonic and push bullets to the max where chamber pressures are running double what they are with a subsonic loading. Even then, what I typically see is an AR cycling back hard and ejecting aggressively but that's about it.

I have probably "opened a can of worms" here with this discussion but there are other perspectives on the issue involved.
His particular event was that the rifle worked great, ejected perfectly, but when he put a suppressor on it it failed. That is why I stated over- gas. If the system is balanced and you double the gas, it may not work well.
 
I see a lot of postings suggesting AR failure to feed malfunctions may be because their rifle is "Over Gassed" and I really have to question this. For backdrop, I have built up and test fired in excess of 500 AR-15's, many of them with custom or wildcat cartridges, and with a myriad of barrel lengths, gas system lengths, etc., where there was no recognized or normally accepted port sizing (had to figure it out).

One of the main arguments of the failure to feed malfunction as relates to "Over Gassing" is that the bolt carrier and bolt speed is too fast.

I have yet to see "Over Gassing" as a source of a failure to feed malfunction to be a real issue for a few reasons:

1. The speed of the carrier and bolt coming forward to feed a round is almost 100% governed by the stiffness of the buffer spring and the weight of the buffer.
2. If a rifle is "Over Gassed", that may speed up the retreat of the carrier and the unlocking of the bolt out of battery, but it does not per se speed up the carrier and bolt coming forward (i.e. the buffer typically hits the back of the buffer tube and the dead plastic end of the buffer softens that strike so it's not metal to metal, but it's not a trampoline effect, nor was an AR buffer system designed to do that).
3. An AR gas system is set up to bleed off all gas immediately after the bolt opens out of battery (i.e. it blows out the vent holes in the side of the carrier) so it's not like the system holds onto excess pressure to somehow convert that into carrier or bolt speed coming forward.

I am also not a big fan of adjustable gas blocks and I have seen plenty of issues with them (taken a bunch of them off customer guns a returned them because they were a source of a problem that did no exist). First off, an adjustable gas block is of no value at all unless the rifle is over ported. All an adjustable gas block can do is cut back the amount of gas being delivered into the gas system from the port, it can never add more than can come through the port. It may have some value for someone that wants to run something like a 300 BO where they want to shoot subsonic "heavies" with a real fast powder through a can to run very quiet (ergo they have a very large port to do that), but then wants to shoot supersonic and push bullets to the max where chamber pressures are running double what they are with a subsonic loading. Even then, what I typically see is an AR cycling back hard and ejecting aggressively but that's about it.

I have probably "opened a can of worms" here with this discussion but there are other perspectives on the issue involved.
I don't know that I've had the occasion to assemble or diagnose that many ARs in my lifetime, but I don't think I agree.

Energy is equal to mass x velocity. Every action produces a reaction. The faster the bolt carrier is moving when it hits the bottom of the buffer tube, the faster it will be moving on the return stroke. If you drop a baseball from waist high onto concrete, it might bounce 4". Drop that baseball from 20 feet high and it will bounce higher. That's because when dropped from 20 feet, it will have attained more velocity by the time it hits the ground and, therefore, will have more energy. Same principal with the bolt carrier group. It isn't just about the spring and weight of the buffer.

In extreme cases, I have seen too much bolt velocity cause an AR to malfunction. You can mitigate this with a heavier spring to bleed off some of the energy of the BCG, but that won't fix the problem of insufficient closed bolt lock time, but that's a whole different discussion.
 
I don't know that I've had the occasion to assemble or diagnose that many ARs in my lifetime, but I don't think I agree.

Energy is equal to mass x velocity. Every action produces a reaction. The faster the bolt carrier is moving when it hits the bottom of the buffer tube, the faster it will be moving on the return stroke. If you drop a baseball from waist high onto concrete, it might bounce 4". Drop that baseball from 20 feet high and it will bounce higher. That's because when dropped from 20 feet, it will have attained more velocity by the time it hits the ground and, therefore, will have more energy. Same principal with the bolt carrier group. It isn't just about the spring and weight of the buffer.

In extreme cases, I have seen too much bolt velocity cause an AR to malfunction. You can mitigate this with a heavier spring to bleed off some of the energy of the BCG, but that won't fix the problem of insufficient closed bolt lock time, but that's a whole different discussion.
I guess I might theoretically agree with you if you put your AR up against a piece of concrete (like your ball bouncing on a concrete floor scenario) and pull the trigger, but most people fire AR's from their shoulder and IMO the shoulder also absorbs the force of the buffer hitting the back of the buffer tube (just like it absorbs the rifle recoil). Scenario in my view is more like a baseball going into a baseball mitt.
 
I see a lot of postings suggesting AR failure to feed malfunctions may be because their rifle is "Over Gassed" and I really have to question this. For backdrop, I have built up and test fired in excess of 500 AR-15's, many of them with custom or wildcat cartridges, and with a myriad of barrel lengths, gas system lengths, etc., where there was no recognized or normally accepted port sizing (had to figure it out).

One of the main arguments of the failure to feed malfunction as relates to "Over Gassing" is that the bolt carrier and bolt speed is too fast.

I have yet to see "Over Gassing" as a source of a failure to feed malfunction to be a real issue for a few reasons:

1. The speed of the carrier and bolt coming forward to feed a round is almost 100% governed by the stiffness of the buffer spring and the weight of the buffer.
2. If a rifle is "Over Gassed", that may speed up the retreat of the carrier and the unlocking of the bolt out of battery, but it does not per se speed up the carrier and bolt coming forward (i.e. the buffer typically hits the back of the buffer tube and the dead plastic end of the buffer softens that strike so it's not metal to metal, but it's not a trampoline effect, nor was an AR buffer system designed to do that).
3. An AR gas system is set up to bleed off all gas immediately after the bolt opens out of battery (i.e. it blows out the vent holes in the side of the carrier) so it's not like the system holds onto excess pressure to somehow convert that into carrier or bolt speed coming forward.

I am also not a big fan of adjustable gas blocks and I have seen plenty of issues with them (taken a bunch of them off customer guns a returned them because they were a source of a problem that did no exist). First off, an adjustable gas block is of no value at all unless the rifle is over ported. All an adjustable gas block can do is cut back the amount of gas being delivered into the gas system from the port, it can never add more than can come through the port. It may have some value for someone that wants to run something like a 300 BO where they want to shoot subsonic "heavies" with a real fast powder through a can to run very quiet (ergo they have a very large port to do that), but then wants to shoot supersonic and push bullets to the max where chamber pressures are running double what they are with a subsonic loading. Even then, what I typically see is an AR cycling back hard and ejecting aggressively but that's about it.

I have probably "opened a can of worms" here with this discussion but there are other perspectives on the issue involved.
How many of the rifles that you are referring to were suppressed?
 
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I'll state up front, I'm no AR expert.

I love to read these discussions because it helps me understand the AR much better.

With that said, I've noticed a pattern when people give their opinions on what causes malfunctions.
They tend to pinpoint three things:
Gas volume.
Buffer weight.
Buffer springs.

Then there's shitty magazines, ill fitting cartridges and just plain pro ammo choices.


Above, ^^^ the discussion is trending towards buffer rearward speed and return to battery speed.

If a piece of brass fails to clear the ejection port then we get double feed, stovepipes, and even sometimes a nearly rear facing piece of brass.

Dirty (filthy or dry) rifles tend to have more malfunctions than properly cleaned and lubed rifles. Of
course we're all aware of that.



Okay, so where the hell am I going with all this?
When a rifle tends to have feeding issues we look at the common causes. Because these are so common, we tend to overlook some small things we take for granted.

All of the pieces have to work in harmony with each other at the correct timing. If a buffer comes back a nanosecond faster than it should, it narrows up the time each part has to do its job properly. The theory being discussed ^^^^ up there, is that the buffer also returns faster, therefore reducing the travel time.

For the sake of discussion, let's agree for a moment that it does move quicker.
Once we speed up the timing, now two more pieces have to also speed up. Those pieces are the extractor and ejector.

The ejector has to quickly (now even more quickly) kick that brass out the little ejection port.

Of course, the ejector can't do it's job correctly if the extractor doesn't do all three of its jobs correctly and in the proper amount of time.
The extractor has to first, pull the brass from the chamber. Next is hold that brass on the bolt face until the case mouth clears the port. Once it clears the port, the ejector tries to flip the brass away while the extractor is pivoting and releasing the brass.

I believe a lot of issues revolve around weak ejector springs and worn/shitty fitting extractor.

You can test your ejector strength (rebound speed) simply by inserting a piece of brass in the bolt face and see how far it flings the brass.
If you want to be scientific about it, pin the BCG or just the bolt face down to a board and fling the brass into sand.




I'd love to be able to do high speed video to test the BCG/buffer speed in relation to gas volume and gas speed.

Along with that, the video could show the operation and speed of different ejector/extractor combinations.



Just my post-second cup of coffee ramblings.
I think I'll go take a dump now.
 
How many of the rifles that you are referring to were suppressed?
Never bothered to count but certainly threaded a lot of AR muzzles for suppressors. Last four I worked on and tested last week were all suppressed. Maybe this is a bit controversial for me to say but IMO if an AR is set up and functioning 100% in the first place, I have never seen a functioning issue arise merely by putting on a suppressor.
 
On ejection, more than once I have seen AR's where the extractor was holding onto the fired brass case and would not freely let it go so that the rifle ejection was compromised. Typically the problem was what I will call the "points" on the sides of extractor that were biting into the rim of the brass and would not let the brass go. With them, I take a triangular stone and stone the extractor to mute those points so they don't dig into the brass - - problem solved!
 
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I'll state up front, I'm no AR expert.

I love to read these discussions because it helps me understand the AR much better.

With that said, I've noticed a pattern when people give their opinions on what causes malfunctions.
They tend to pinpoint three things:
Gas volume.
Buffer weight.
Buffer springs.

Then there's shitty magazines, ill fitting cartridges and just plain pro ammo choices.


Above, ^^^ the discussion is trending towards buffer rearward speed and return to battery speed.

If a piece of brass fails to clear the ejection port then we get double feed, stovepipes, and even sometimes a nearly rear facing piece of brass.

Dirty (filthy or dry) rifles tend to have more malfunctions than properly cleaned and lubed rifles. Of
course we're all aware of that.



Okay, so where the hell am I going with all this?
When a rifle tends to have feeding issues we look at the common causes. Because these are so common, we tend to overlook some small things we take for granted.

All of the pieces have to work in harmony with each other at the correct timing. If a buffer comes back a nanosecond faster than it should, it narrows up the time each part has to do its job properly. The theory being discussed ^^^^ up there, is that the buffer also returns faster, therefore reducing the travel time.

For the sake of discussion, let's agree for a moment that it does move quicker.
Once we speed up the timing, now two more pieces have to also speed up. Those pieces are the extractor and ejector.

The ejector has to quickly (now even more quickly) kick that brass out the little ejection port.

Of course, the ejector can't do it's job correctly if the extractor doesn't do all three of its jobs correctly and in the proper amount of time.
The extractor has to first, pull the brass from the chamber. Next is hold that brass on the bolt face until the case mouth clears the port. Once it clears the port, the ejector tries to flip the brass away while the extractor is pivoting and releasing the brass.

I believe a lot of issues revolve around weak ejector springs and worn/shitty fitting extractor.

You can test your ejector strength (rebound speed) simply by inserting a piece of brass in the bolt face and see how far it flings the brass.
If you want to be scientific about it, pin the BCG or just the bolt face down to a board and fling the brass into sand.




I'd love to be able to do high speed video to test the BCG/buffer speed in relation to gas volume and gas speed.

Along with that, the video could show the operation and speed of different ejector/extractor combinations.



Just my post-second cup of coffee ramblings.
I think I'll go take a dump now.
No, you're right. Gas volume, buffer weight and spring rate are the topics of many discussions. Those discussions often start with ... " so, I built this AR and ....."

I honestly believe that the topics of buffer weight and spring rate come up so often because people like to tinker and for many people, a little knowledge is a dangerous thing. Spring rate and buffer weight are two things that someone with very little knowledge can muck with. Fortunately, messing with those two things don't usually result in a catastrophic failure.

On the other hand, gas volume, spring rate and buffer weight are at the heart of the proper operation of an AR. Assuming a conglomeration of good working parts, an AR can be rendered inoperable with a bad combination of the three.

What many fail to understand is how those three things interact with each other and what the main goal is. The main goal being an optimal closed bolt lock time.

What really doesn't help is all of the companies selling springs for obscene prices using ejection pattern as a selling point. Truth is that spring rate has very little to do with closed bolt lock time, but can make you think that you're accomplishing something because the ejection pattern changed. At that point, all you'll likely have is an overgassed rig with too little closed bolt lock time that has a good ejection pattern.
 
No, you're right. Gas volume, buffer weight and spring rate are the topics of many discussions. Those discussions often start with ... " so, I built this AR and ....."

I honestly believe that the topics of buffer weight and spring rate come up so often because people like to tinker and for many people, a little knowledge is a dangerous thing. Spring rate and buffer weight are two things that someone with very little knowledge can muck with. Fortunately, messing with those two things don't usually result in a catastrophic failure.

On the other hand, gas volume, spring rate and buffer weight are at the heart of the proper operation of an AR. Assuming a conglomeration of good working parts, an AR can be rendered inoperable with a bad combination of the three.

What many fail to understand is how those three things interact with each other and what the main goal is. The main goal being an optimal closed bolt lock time.

What really doesn't help is all of the companies selling springs for obscene prices using ejection pattern as a selling point. Truth is that spring rate has very little to do with closed bolt lock time, but can make you think that you're accomplishing something because the ejection pattern changed. At that point, all you'll likely have is an overgassed rig with too little closed bolt lock time that has a good ejection pattern.

So you're saying someone HAS invented a brass stretcher? 😆
 
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I guess I might theoretically agree with you if you put your AR up against a piece of concrete (like your ball bouncing on a concrete floor scenario) and pull the trigger, but most people fire AR's from their shoulder and IMO the shoulder also absorbs the force of the buffer hitting the back of the buffer tube (just like it absorbs the rifle recoil). Scenario in my view is more like a baseball going into a baseball mitt.
That would dictate that potential malfunctions would change whether the rifle is fired standing unsupported, seated/in a rest, or while standing and clamped/locked into a tripod? So, this sort of malfunction would be more common while seated/in a rest as that's the most rigid system and thus would maintain the most energy in the system through the complete process, with less malfunctions while in a standing unsupported position as there's a higher damping factor (the rifle clamped in a Ransom rest or similar as the "worst-case" rigid system and 100% free recoil being the least severe high-damped system).

Does that show up in field evals investigating malfunctions related to gas volume and BCG speed?
 
...I have never seen a functioning issue arise merely by putting on a suppressor.
I have. Twice. In both cases an AGB fixed it. Latest was a buddies 18" 556 with mid-length gas. It seemed a bit over-gassed in the first place, but was functional. Then he threw a suppressor on, and started having "jamming" (I forget what exactly was happening) issues. We put an adjustable gas block on and tuned it, and it's been problem free since.
 
How many adjustable gas blocks has Colt put on mil speck M16s ?
Ok... they're made to a certain "spec", which usually even includes what ammo they're going to use. Pretty easy to dial that in.
Throw a high back pressure can on the end and see how they run...

There are a number of factors (barrel length, gas system length, port size, etc) involved in the gas system. Certainly, it's possible to line all those up in a way where the rifle is functional both with and without a suppressor, but you're probably going to be on the edges of reliability.
 
Only when firing fissionable material.
Momentum (p) = M x V
Energy = M/2 x V^2
You're right. I knew I left a step out when I punched it into the keyboard. If I had the math, I'd be one designing the stuff that others would be trying to figure out.

Still, I think that the gist of what I was saying holds. The velocity of the BCG on the forward stroke is affected by the velocity of the BCG on the rearward stroke.
 
Never bothered to count but certainly threaded a lot of AR muzzles for suppressors. Last four I worked on and tested last week were all suppressed. Maybe this is a bit controversial for me to say but IMO if an AR is set up and functioning 100% in the first place, I have never seen a functioning issue arise merely by putting on a suppressor.
I can't say right or wrong but have read many posts saying running suppressed cause cycling problems and gas in the face. No doubt they run dirty but im shooting a 223, Valkyrie, 6 ARC, 22-250, 243, 6.5 Creedmoor, 7mm-08 and a 308 and only had to turn the gas down on the 22-250 2 clicks, the rest shoot like they did without a suppressor. It's a 9 baffle can so not a flow through. Not what I was expecting but good with the results.
 
Never bothered to count but certainly threaded a lot of AR muzzles for suppressors. Last four I worked on and tested last week were all suppressed. Maybe this is a bit controversial for me to say but IMO if an AR is set up and functioning 100% in the first place, I have never seen a functioning issue arise merely by putting on a suppressor.
Not getting in a pissing match, I was asking for a point of reference. I do disagree with your response about the suppressor not causing the issue, dirty is always an issue. Once again for reference, when you refer to testing is that 5 rounds 500 rounds?
 
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This thread is a prime example of the complexities that come along with running a gas gun and many of those complexities are often over simplified.

Can an overgassing situation cause feeding and ejection malfunctions? I think so. Over gassing causes excessive bolt velocity, but I think the more important issue is insufficient closed bolt lock time. Too short of a lock time leads to ineffective extraction and, subsequently, ejection.

Overgassing causing problems, or beginning to cause problems can usually be seen upon inspection of ejected or even stuck casings. You can see the stretching or tearing of case heads from the system trying to extract before pressure subsides and the case shrinks.

Overgassing problems can also be exacerbated by the addition of a suppressor. A few have posted that they have encountered no issues with the addition of a suppressor, but the calibers being mentioned would lead me to believe that they are talking about rifle setups. What I mean by a rifle setup is something running an 18" or longer barrel and running a rifle length or longer gas system.

In my experience, however limited, tuning a 10.5" carbine gas 5.56 to run an old fashioned baffle stack can is a whole different animal from trying to get a 20" rifle length gas with a flow through can to run right. The shorter the gas system, the smaller the operational window is. You're dealing with much higher pressures with a carbine gas system than you are with a rifle length gas system.
 
My experience with over gassed was the bcg was moving rearward so soon the extractor was almost tearing the rim off the case. It would get the occasional feed the next round, before the first was ejected. Installed an AGB and a heavier buffer and it was much better with little to no marks on the case rim at all. Most likely too large of a gas port from the manufacturer.... to make sure it would eject.... I have no idea if these problems can be pinned down to a single item or several mis-matched ones.... With my 308AR I have an AGB, heavier buffer and spring. Runs perfectly and the case rims on the brass looks like it came out of a bolt gun. I assume the bolt lock time is in the "happy zone".
 
1. The speed of the carrier and bolt coming forward to feed a round is almost 100% governed by the stiffness of the buffer spring and the weight of the buffer.
The greatest success I’ve had solving gas gun problems are this and turning up the gas.

I haven’t seen over gassed equating to malfunctions, personally.

I also prefer non adjustable gas blocks.
 
This thread is a prime example of the complexities that come along with running a gas gun and many of those complexities are often over simplified.

Can an overgassing situation cause feeding and ejection malfunctions? I think so.

I think this is well put.

Gassing changes the dynamic of how the system functions. Changes in the system or how the system functions has a ripple effect on other components in the system and create consequences.

Ultimately, we have learned a lot but I don't think we're at the finish line. Just this morning I was listening to some of the lessons being learned from the 6.8 high-pressure ngsw stuff