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Over gassing an AR and the problems is causes


Dolomite_supafly

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99% of all the cycling issues with an AR are related to the gun being over or under gassed. An under gassed gun is easy to diagnose but an over gassed gun is much harder to find.

 

What is over gassing? It is when the bolt is unlocked prematurely when the barrel pressures are still relatively high. It can becaused by a few things but the biggest cause is a gas port that is way over sized for the port position.The industry has embraced the idea that a over gassed gun is a reliable gun. But that is just not the case. When the same industry began to realize this they introduce heavy weight buffers to mend the problems of their over gassed guns.

 

When an AR is over gassed the bolt speed increases and this can cause rounds to not be picked up or the bolt not locking back on an empty magazine. It can also effect how well the gun ejects the spent rounds. Both of these problems are problems wth reliability.

 

An over gassed gun will also reduce the velocity because the bolt is unlocking while there is still more pressures in the barrel. Those additional pressures are used to vercome the resistance of the bullet and increase velocity. Once a bullet is moving is doesn't take much to keep it moving so any amount of gas bleed off by a over gassed system reduces teh velocity.

 

Another issue, the biggest IMHO, with over gassed guns is they run much dirtier because of the extra pressures still in the barrel at the time the bolt unlocks. Also, the additional gas being forced down the gas tube only adds to the large amount of crud in the upper receiver. And all this extra crud causes reliability issues. This is why everyone says to run an AR wet, it is not because an AR needs the extra lubrication but because it helps suspend the crud and this helps the cruddy gun run. I have had one of my guns go well over 1,000 rounds without cleaning or lube. It ran an adjustable gas block that was set to the minimum gas impulse to run. A properly gassed gun will shoot thousands of rounds between cleanings. And it will do so with a minimal amount of lubrication as well.

 

Another problem is premature wear on the locking lugs. When a gun is properly gassed the amount pf pressure on the locking lugs as they clear the corner is minimal comparted to when a gun is over gassed. Although it will take a long time to become an issue it is still an issue.

 

And finally, having a properly gassed gun will reduce the felt recoil. What, how can that possibly be? Well when a gun is over gassed the bolt unlocks earlier than is should when the pressures and gas volume are still higher than they should be. The additional pressures and volume exert more force upon the bolt and buffer. When this happens it increases their speed as they travel rearward. And then those fast moving buffers and bolts come to an abrupt stop as they impact the rear of the buffer tube very hard. And this impact is felt as a strong jolt that most confuse with recoil. An AR should have the same recoil as a bolt action that weighs the same or even less felt recoil because the impulse is lengthened because of the semi automatic action. But in most cases the AR will have a harder recoil impulse. And if you want to see a difference disable the gas system on your AR and shoot it, you might be surprized at how light the recoil actually is.

 

These are the reason why people say a midlength gas gun recoils softer. It is because they have more volume in the barrel to reduce the pressues before the bolt unlocks. And that is why rifle length systems are generally the softest shooting guns. Take an old A1 that weighs less than most modern M4's and the A1 will have less of a recoil impulse than the M4. The reason why is the bolt speed is much slower on the rifle length gas system of the A1 than the on the carbine length gas system of the M4.

 

I recommend this to everyone, even if they think their gun isn't over gassed. I recommend they install an adjustble gas block and tune their gun. It offers a lot of advantages that people don't think about without any detractors. It reduces recoil, keeps the gun clean, makes the gun more reliable and reduces wear and tear. People spend a lot of money on fancy muzzle brakes and flash hiders to reduce recoil when an adjustable gas block could accomplish a lot of the same effects. Shootign an AR with an adjustable gas block AND a muzzle brake is 22 lr like in recoil.

 

In the industry's quest to build a better gun they have made it much worse than Gene Stoner's original design. Gene developed a lightweight gun that was both effective AND reliable. It was when the industry began monkeying with it that both of those attributes were taken away. If you have ever shot an original A1 against a modern M4 you will understand completely.

 

Dolomite

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<blockquote class='ipsBlockquote'data-author="graycrait" data-cid="863926" data-time="1355970687"><p>
Now I need an adjustable gas block on my 20" HBAR - grrrrr.....</p></blockquote>

Adj gas block on 20" HBAR? I guess you could put one on it if you really wanted too, but you shouldn't need it.

My 20" HBAR is the smoothest, softest recoiling centerfire rifle that I own.
Link to comment
<blockquote class='ipsBlockquote'data-author="graycrait" data-cid="863926" data-time="1355970687"><p>
Now I need an adjustable gas block on my 20" HBAR - grrrrr.....</p></blockquote>

Adj gas block on 20" HBAR? I guess you could put one on it if you really wanted too, but you shouldn't need it.

My 20" HBAR is the smoothest, softest recoiling centerfire rifle that I own.

 And the reason why is it is probably properly gassed. even if the ports were a little larger than they should be the longer gas system reduces the pressures compared to a carbine or midlength gas system.

 

It is possible to take a carbine length gas system and make it shoot as smoothly as a rifle length gas system. With an adjustable gas block you can lengthen the gas system by reducing the carbine length gas systems pressures to the same pressure as a rifle length gas system. This slows the bolt velocity down to a point where the rearward impact is significantly less.

 

 Dolomite

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