AR10 overgassed?

AR10 overgassed?

This is a discussion on AR10 overgassed? within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; A short while back, a guy came up to me at the range and told me my Barrett Rec 10 (AR10 )was overgassed. He did ...

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Thread: AR10 overgassed?

  1. #1
    VIP Member Array G26Raven's Avatar
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    AR10 overgassed?

    A short while back, a guy came up to me at the range and told me my Barrett Rec 10 (AR10 )was overgassed. He did not explain why he thought this to be true, and I was not having any functional issues with the rifle. I presume he thought the rifle was throwing brass too far, but I am not really sure.

    I've looked up articles about this issue and there seems to be a wide range of "solutions," ranging from adding an adjustable gas block, to changing the buffer and spring, to changing the ammo.

    I am shooting a Nosler Accubond 150 grain bullet with 44.5 grains of Varget behind it. My muzzle velocity averages 2643 FPS. I've included one of my hunting practice targets from last fall, below.

    Short of taking the rifle to the local gunsmiths and letting them test it, I am not sure how to proceed? Do our AR experts here have any suggestions.

    AR10 overgassed?-target-2.jpg
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  2. #2
    VIP Member Array Havok's Avatar
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    I haven't seen the rifle or anything, but you're not exactly shooting an inexpensive, low quality rifle. I would think Barrett knows more about what they are doing than the guy at the range who most likely(generally speaking of course) learned everything he knows on youtube. If you're concerned, I would contact Barrett. Lots of dudes have been killed overseas by guys with rifles that are "overgassed".
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    I have a DPMS LR-10 and though not the quality of your Barrett, it is a nice rifle and works well.
    It also throws the brass out a bit far but I never thought about it. It cycles well is very accurate and has zero jams so i am not going to worry about it.
    The only thing that is overgassed is myself.

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    "Over-gassed" isn't a problem in itself and is usually on purpose to enable reliability under varied conditions and with a wide spectrum of ammo. With 7.62/.308, there is a pretty big range, just like with 5.56 and .223.

    I've no doubt that the gas port on a .308AR is sized to accommodate the lower pressure 7.62 ammo, probably some low quality surplus stuff to boot, VS the higher pressure .308 loads. The real results is extra recoil and it's harder on your rifles components. Really not a big deal, unless it's a match rifle used in some sort of timed and accuracy event.

    IF I wanted to "fix" it (it's not really broken, just not ideal for a specified ammo) I'd look at an adjustable gas block VS a heavier buffer & spring. IF the gun isn't exhibiting any feeding or ejection issues now, the buffer and spring are fine. It's much easier to adjust the gas using an AGB, based on the ammo than swap out parts.
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    He probably noted which clock direction the cases were ejecting. A "properly" gassed AR ejects about 3:00-4:00 direction from the ejection port. More toward 1-2:00 is undergassed, more toward 5-6 is overgassed. Of course, many things affect the ejection direction besides gas port size--buffer spring strength, buffet weight, cartridge pressures, etc.

    Is it a problem? Maybe . . . maybe not. If several different loads are ejecting really rearward, it can be. A heavier buffer spring is often the easy remedy. Maybe a different buffer. Both are relatively cheap. And adjustable gas port will also allow the ejection angle to be varied, but usually those are more needed with gun that use suppressors.

    Some AR makers intentionally lean toward overgassing to avoid feeding/short-stroking. But it shouldn't be extreme.

    I'd make a note of what clock direction your cases are going and work from there. You may need nothing at all.
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    VIP Member Array G26Raven's Avatar
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    I went to the range on Wednesday and indeed, the Barrett is running well, but it it ejecting the cases at 1:00. This would be "under-gassed" as OldVet explained. I called Barrett today and talked to them and they told me that as long as the rifle was not malfunctioning by doubling or failing to eject, I should not be concerned. They said if there were performance or reliability issues, they would fix it.

    Given the stoutness of the components, I can't say I am concerned that this rifle will be less than reliable. And it shoots well. The target below is from 200 yards, shooting 150 grain Nosler Accubonds.

    AR10 overgassed?-target.jpg
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    Yep, don't fix what don't need fixin'. The only problem you might run into is short-stroking with light loads.
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    Typical gun range bozo. Ignore him. You got the straight story here.

    Anyone who thinks they can tell when a rifle is in a particular state without actually sitting down and looking in detail is not worth listening to.
    "The difference between genius and stupidity is that genius has limits."

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    The only thing worse than "good enough" is "better."

    If the gun runs reliably, it would appear it is gassed properly.
    bmcgilvray and G26Raven like this.

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    Your range guy who nosed into your business with his unsolicited comments is over-gassed.

    Maybe he can't help it. Maybe he ate too many bean burritos for lunch. If he comes nosing around again, tell him about these.

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  12. #11
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    Quote Originally Posted by G26Raven View Post
    A short while back, a guy came up to me at the range and told me my Barrett Rec 10 (AR10 )was overgassed. He did not explain why he thought this to be true, and I was not having any functional issues with the rifle. I presume he thought the rifle was throwing brass too far, but I am not really sure.

    I've looked up articles about this issue and there seems to be a wide range of "solutions," ranging from adding an adjustable gas block, to changing the buffer and spring, to changing the ammo.

    I am shooting a Nosler Accubond 150 grain bullet with 44.5 grains of Varget behind it. My muzzle velocity averages 2643 FPS. I've included one of my hunting practice targets from last fall, below.

    Short of taking the rifle to the local gunsmiths and letting them test it, I am not sure how to proceed? Do our AR experts here have any suggestions.

    Click image for larger version. 

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    Nice 200 yard target by the way and that sounds like a good load.
    G26Raven likes this.
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