Overgassed when suppressed

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  • Ben Karns

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    Dec 2, 2017
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    Covington, LA
    Just put a 10.3 BA Hanson profile barrel with pinned gas block in this new pistol upper I built. See pictures if you are interested in barrel length to handguard spacing. 9.25" handguard.

    Unsuppressed the weapon functions great and ejects to the 3-4 o'clock. Suppressed it is overgassed ejecting to the 1oclock (not a shocker, I was expecting this)

    Question, how do I mange the gas without getting an adjustable gas block when shotting suppressed? I am also not interested in having 2 uppers for Unsurpressed and suppressed shooting either.

    Thanks BS!
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    dk.easterly

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    You sure it's overgassed? I used an identical setup with the Geissele Super 42 buffer/spring and it was too much. Caused all sorts of malfunctions. Put a standard carbine setup in and it runs like a top now.
     

    rcm192

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    Subscribed. MGI makes a Dfender oring for the extractor claw. I know that wont fix over gassing but it could fix ejection patterns. I am in process of doing a 10.5" faxon barrel build with a strike ind viper pdw stock that has a proprietary buffer/spring combo. My 7.5" upper runs but I dont supress it. So I will be sure to post my findings here when done.
     

    shrxfn

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    Not sure why you would not want to get an adjustable gas block. It would make the rifle recoil less and it saves dumping all the extra gas down the pipe and into your upper. most good adjustable gas blocks have an adjustment screw that clicks when you move it so you set it to the minimum gas needed for cycling suppressed then take off the suppressor and then count the clicks you had to make to get it to cycle unsuppressed and then move back and forth between them for shooting either way. You don't have to have 2 uppers although with my setup I am never going to shoot unsuppressed anymore so I set it for suppressed cycling and am forgetting about it that is why god created QD mounts for the suppressors.
     

    leadslinger972

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    Not sure why you would not want to get an adjustable gas block. It would make the rifle recoil less and it saves dumping all the extra gas down the pipe and into your upper. most good adjustable gas blocks have an adjustment screw that clicks when you move it so you set it to the minimum gas needed for cycling suppressed then take off the suppressor and then count the clicks you had to make to get it to cycle unsuppressed and then move back and forth between them for shooting either way. You don't have to have 2 uppers although with my setup I am never going to shoot unsuppressed anymore so I set it for suppressed cycling and am forgetting about it that is why god created QD mounts for the suppressors.

    One reason may be that he prefers not to disassemble the rifle to install a gas block. Another reason may be the fact that adjustable gas blocks are a bandaid for improperly sized gas ports. If you can't get it to cycle properly by changing out buffer weights and springs, it's highly likely that the gas port is over sized.
     

    Ben Karns

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    One reason may be that he prefers not to disassemble the rifle to install a gas block. Another reason may be the fact that adjustable gas blocks are a bandaid for improperly sized gas ports. If you can't get it to cycle properly by changing out buffer weights and springs, it's highly likely that the gas port is over sized.
    ^^correct

    I'll most likely go the heavy buffer route. Seems to be the cheapest, easiest, quickest option which is what I'm looking for now. Will look for a more permanent solution in the future.

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    Ben Karns

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    You sure it's overgassed? I used an identical setup with the Geissele Super 42 buffer/spring and it was too much. Caused all sorts of malfunctions. Put a standard carbine setup in and it runs like a top now.
    Suppressed it is for sure overgassed. 1 o'clock ejection is a symptom of that all day. Are you running suppressed?

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    dk.easterly

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    I'm not running suppressed. However with that setup I was having overgassed symptoms. Forward ejection patterns. Soon as I changed the buffer/spring, it has run great ever since.

    Also, the BA Hanson barrels use a 0.076" gas port.
     

    oldsman350

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    Aug 25, 2010
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    I’ve got a 10.3* MK18 and I installed the VLTOR A5 buffer system and a ported charging handle best move ever. Had to change out to the VLTOR rifle length buffer tube, Green SpringCo spring and a heavy buffer. Originally had a PSA 11 upper that shot gas all over my face when shooting suppressed. Now that I’ve got the MK18 upper and the VLTOR system and ported charging handle I have yet to get any gas in my face. Plus the recoil has softened a little as well.
     

    Bmash

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    Dec 23, 2013
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    jcomr1 already mentioned the Gemtech adjustable gas block. I put one on a 300 BO SBR and it seems to have helped. (I use a brass catcher so I haven't seen where the brass throws) I run this gun suppressed and unsuppressed with subsonic and supersonic. It ran ok before the change, but it sure helped my brass have less dents/damage.
     

    jdindadell

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    No so sure I can agree that an adj gas block is a bandaid fix for an oversized gas port...

    Just about every fixed (non adjustable) gas operated design out there is overgassed by design to cope with the alarming number of variables. The AK is well known to be overgassed, and my experience with the ar indicates that too.

    If you plan to run any sort of non std setup (suppressed, weird length barrel, non std buffer, etc, etc) having a adj gas system is a good idea, and possibly necessary. I have always found humor in adding weight to the buffer (and thus increasing the reciprocating weight of the action) to "fix" some sort of issue, when the problem is too much gas. I can understand the need in a blowback 9mm ar, as that is the only tuning aid. However adding weight to the moving part will up the felt recoil and would it not be better to decrease the gas? Plus you have to be able to slow, stop, and redirect all of this added mass, which does add strain and thus wear to the system.

    I understand why the original ar was built with a fixed gas system, but that was 70yrs ago. Ammo, setups, shooting styles, etc have all changed.

    Sure, setting a gun up to "just" run a specific round is a bad idea if you plan to use this to save your life during the zombie apocalypse. However, being able to tune the gas system to account for the variable is a great idea...

    Rubber city make an adjustable gas key for the BCG. Given the low cost of a decent BCG you could always just buy a spare (not a bad thing to have in any case), install and tune the adjustable gas key to run suppressed and then swap it with the stocker when you want to run un-suppressed. Plus if you plan to play with the loads you have another tuning tool, not a bag of buffers filled with unobtanium. And you can run a std carbine buffer, 30z or so, and have a smoother shooting rifle.
     

    leadslinger972

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    No so sure I can agree that an adj gas block is a bandaid fix for an oversized gas port...

    Just about every fixed (non adjustable) gas operated design out there is overgassed by design to cope with the alarming number of variables. The AK is well known to be overgassed, and my experience with the ar indicates that too.

    If you plan to run any sort of non std setup (suppressed, weird length barrel, non std buffer, etc, etc) having a adj gas system is a good idea, and possibly necessary. I have always found humor in adding weight to the buffer (and thus increasing the reciprocating weight of the action) to "fix" some sort of issue, when the problem is too much gas. I can understand the need in a blowback 9mm ar, as that is the only tuning aid. However adding weight to the moving part will up the felt recoil and would it not be better to decrease the gas? Plus you have to be able to slow, stop, and redirect all of this added mass, which does add strain and thus wear to the system.

    I understand why the original ar was built with a fixed gas system, but that was 70yrs ago. Ammo, setups, shooting styles, etc have all changed.

    Sure, setting a gun up to "just" run a specific round is a bad idea if you plan to use this to save your life during the zombie apocalypse. However, being able to tune the gas system to account for the variable is a great idea...

    Rubber city make an adjustable gas key for the BCG. Given the low cost of a decent BCG you could always just buy a spare (not a bad thing to have in any case), install and tune the adjustable gas key to run suppressed and then swap it with the stocker when you want to run un-suppressed. Plus if you plan to play with the loads you have another tuning tool, not a bag of buffers filled with unobtanium. And you can run a std carbine buffer, 30z or so, and have a smoother shooting rifle.

    If the gas port is oversized, everything is a band aid.
     

    leadslinger972

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    If you plan to run any sort of non std setup (suppressed, weird length barrel, non std buffer, etc, etc) having a adj gas system is a good idea, and possibly necessary. I have always found humor in adding weight to the buffer (and thus increasing the reciprocating weight of the action) to "fix" some sort of issue, when the problem is too much gas. I can understand the need in a blowback 9mm ar, as that is the only tuning aid. However adding weight to the moving part will up the felt recoil and would it not be better to decrease the gas? Plus you have to be able to slow, stop, and redirect all of this added mass, which does add strain and thus wear to the system.

    Increasing buffer weight actually reduces felt recoil. Heavier buffer weights reduce bolt speed, and tremendously help bolt bounce (although most people don't care about that).

    It's always better to decrease the volume/pressure of gas, but an adjustable gas block isn't THE solution. Heavier buffer weights and springs can slow the bolt down enough to offset any overgassing issues. The issue comes with what to do with the excess gas when suppressed. There are ways to vent the gas, rather than restricting it.
     

    jdindadell

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    If the gas port is oversized, everything is a band aid.

    True, but aside from getting a barrel without a gas port or undersized and incrementally enlarging it while testing, how do you tune for a wide variety of ammo and/or setup changes? And once you have it working using that method, you are stuck running the gun that way, as you do not have any adjustability.

    Increasing buffer weight actually reduces felt recoil. Heavier buffer weights reduce bolt speed, and tremendously help bolt bounce (although most people don't care about that).

    I can see this applying in an overgassed situation, but I still feel that adjusting the gas volume is a better way to slow down the speed and thus balance the system. I have looked into bolt bounce a little (basically like striking something solid with a hammer, unless it is "shot loaded" it will bounce) and it does appear that a heavier buffer (the moveable weights inside the buffer are heavier) will help to mitigate this, however a weaker spring and less overall mass will help too, as illustrated by swinging a lighter hammer slower. Slowing down the bolt too much can cause feeding issues on the closing stroke, so this is a balancing act. Given that the original m16 rifle buffer was around 5.2 ounces, perhaps the std M4 3oz buffer is underweight any way. I do see that Slash recommends a 6.5oz buffer for an unsupressed carbine. Perhaps the 3oz paradigm is wrong?

    It's always better to decrease the volume/pressure of gas, but an adjustable gas block isn't THE solution. Heavier buffer weights and springs can slow the bolt down enough to offset any overgassing issues. The issue comes with what to do with the excess gas when suppressed. There are ways to vent the gas, rather than restricting it.

    I do agree that there is adjustment capability in the buffer and spring area. And for some people and some setups and adjustable gas block or other adjustable method are not feasible. A gas bleed concept, such as the one from superlative arms sounds like the way to go for suppressed shooting as it does not restrict as a normal adjustable gas system does, it actually dumps the excess gas outside of the block. I have one for testing with my lightweight build, which features a lightened bcg and a 1oz buffer, I also have a rubber city adj gas key to try out. I do not plan to run suppressed, but I have removed about 5-6oz from the bcg/buffer so a reasonable difference.
     

    leadslinger972

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    I'll put it in the simplest terms. There are thousands of suppressed rifles in service that do not require an adjustable gas block.

    Mk18's are notoriously overgassed and run properly without an adjustable gas block.
     

    shrxfn

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    If you tune your rifle to a certain setup using the gas port then yes you can do that. If you don't want to mess with it then get an adjustable gas block. If you are over gassed it has to go somewhere and it is usually out the charging handle unless you do a gas buster style charging handle then it just traps the gas in the upper receiver. If you use an adjustable gas block then you stop the excess gas from ever leaving the barrel and voila it is fixed and you can manipulate the gas as you see fit without having to drill holes bigger or tryng to make a large hole smaller. It is not a band aid it is an intelligent fix to a known existing problem. Most manufacturers build their rifles with oversized ports so that their rifles work with a variety of ammo.

    If you want to put in heavier buffers and springs to fix gas issues then more power to you but these days the first thing I do is take off the GB and put on a adjustable GB as it works for me and my rifles have minimal recoil and gas blowback suppressed.
     
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