"Over Gassed" AR's Fact or Fiction? Other Perspectives
- Thread starter Flexible Tangerine Sprite
- Start date
For op to flex on us with all his experience but clearly be wrong in the end… some guns need gas adjustment end of story. Dude can flex all his military experience he wants but real world use tells a different story.
Sure guns spec’d with the correct port size for an appropriate application will not need any tuning. Others will definitely need tuning.
Didn't read the thread but will throw out my experience.
First off, I will concede that under-gassing or over-springing or over-weighting the buffer will cause more feed problems than over-gassing. You see this a lot in 3-gun and other comps where guys are trying to run the ragged edge and reduce recoil. That said, at some point, increasing the gas will 100% cause feeding, stove pipe, and ejection problems. Somewhere in the abyss I have high-speed footage that shows as much.
The lateral velocity of the ejecting case is pretty much constant and is determined by the ejector plunger spring and the ability of the extractor to properly keep hold of the case. As you increase gas, the rearward velocity component increases and the ejection angle changes, becoming more shallow. Eventually you start hitting the brass deflector (no big deal, still ejects 3:00-4:00), and then as you keep adding gas your cases smack the rear of the ejection port before they can clear the ejection port. This is when you start seeing 12:30-2:00 ejection. Keep adding gas and the cases will hit the rear of the ejection port then fly back into the upper. Sometimes you get extractor issues here, too, with the increased rearward velocity.
Bolt carrier velocity and the impulse of the BCG bottoming out causes a dynamic response to the rest of the system. Sometimes it's no big deal, sometimes, especially with sloppy magazine wells or lowers that hold the magazine at a lower height it definitely can cause feeding problems. The root issue is probably more the loosey goosey magazine well, but excessive recoil/gas isn't helping.
From an accuracy standpoint, I also have documented an increase in the frequency and the severity of fliers when increasing gas to the system.
I am firmly of the opinion that you want as little gas as is necessary to 100% function the system in the range of cleanliness/lube/temp/weather conditions you'll experience unless accuracy isn't on the priority list then gas it up to the point that you avoid the afore-mentioned function problems.
YMMV.
First off, I will concede that under-gassing or over-springing or over-weighting the buffer will cause more feed problems than over-gassing. You see this a lot in 3-gun and other comps where guys are trying to run the ragged edge and reduce recoil. That said, at some point, increasing the gas will 100% cause feeding, stove pipe, and ejection problems. Somewhere in the abyss I have high-speed footage that shows as much.
The lateral velocity of the ejecting case is pretty much constant and is determined by the ejector plunger spring and the ability of the extractor to properly keep hold of the case. As you increase gas, the rearward velocity component increases and the ejection angle changes, becoming more shallow. Eventually you start hitting the brass deflector (no big deal, still ejects 3:00-4:00), and then as you keep adding gas your cases smack the rear of the ejection port before they can clear the ejection port. This is when you start seeing 12:30-2:00 ejection. Keep adding gas and the cases will hit the rear of the ejection port then fly back into the upper. Sometimes you get extractor issues here, too, with the increased rearward velocity.
Bolt carrier velocity and the impulse of the BCG bottoming out causes a dynamic response to the rest of the system. Sometimes it's no big deal, sometimes, especially with sloppy magazine wells or lowers that hold the magazine at a lower height it definitely can cause feeding problems. The root issue is probably more the loosey goosey magazine well, but excessive recoil/gas isn't helping.
From an accuracy standpoint, I also have documented an increase in the frequency and the severity of fliers when increasing gas to the system.
I am firmly of the opinion that you want as little gas as is necessary to 100% function the system in the range of cleanliness/lube/temp/weather conditions you'll experience unless accuracy isn't on the priority list then gas it up to the point that you avoid the afore-mentioned function problems.
YMMV.
FWIW.... I worked on a CLGS 16", with a gas port size of over .100 ( biggest pin gauge I had. )..... guess what the problem was ?
The over sized gas port was breaking the hammer pin in half. The BCG was slamming it so hard !
The OEM one was broke in clear in half when I got it. I told the owner to get a proper gas ported barrel and I will replace it for him.
He and his buddies had all bought the same AR from the same local company... one by one, same issue 3X.
I agree with this. A vast majority of gassing problems are likely user induced. Too much buffer and/or too much spring.
For all of those guys out there that treat the AR platform as though they are playing with tinker toys, it's really handy to have a set of pin gauges. To say that you've assembled these parts and then post questions regarding which buffer and or spring to go with is almost like shooting in the dark (without NV). If you post those same questions with some information, like the size of your gas port, diagnosis would be a lot easier.
For common calibers, like 5.56, you can usually tell with a higher degree of certainty, what the proper buffer weight will be, if you know the gas port size.
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