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Thread: Suppressor backpressure = more noise at shooter's ear?

  1. #1
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    Suppressor backpressure = more noise at shooter's ear?

    Question for those with a bit more suppressor knowledge than myself. Does increased suppressor backpressure typically equate to slightly higher decibel levels at the shooter's ear? In other words, if comparing two 5.56mm suppressors of roughly the same length and diameter, but one exhibits more backpressure on the rifle than the other, will the "gassier" suppressor lead to slightly higher decibel levels from the shooter's perspective?

    With that in mind, since direct impingement guns vent excess gas at the ejection port and piston guns typically vent excess gas at the gas block, could one reasonably expect slightly better at ear performance from a piston gun over DI? Conversely, I suspect DI would have better numbers at the muzzle. Think suppressor optimized piston gun like the 416A5 versus an optimized suppressor ready DI gun like the SR16.

    I ask these questions with the understanding the a lot of variables like ammunition and rifle type come into play here. Thanks in advance gents.


    Tspeis

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    It doesn't matter if it's a normal AR15 or a piston setup. For instance, older 10.3" 416s (before vented/adjustable gas blocks) are notorious for being poor suppressor hosts.

    Higher backpressure suppressors cause the bolt to unlock sooner and increase bolt velocity. This leads to more gas and noise coming out of the ejection port, increasing the sound levels at the shooters ear. The trick is to balance the ejection port sound level with the muzzle sound level, sampled at the shooter's ear.
    Will - Owner of Arisaka LLC - http://www.arisakadefense.com

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    Quote Originally Posted by Slippers View Post
    It doesn't matter if it's a normal AR15 or a piston setup. For instance, older 10.3" 416s (before vented/adjustable gas blocks) are notorious for being poor suppressor hosts.

    Higher backpressure suppressors cause the bolt to unlock sooner and increase bolt velocity. This leads to more gas and noise coming out of the ejection port, increasing the sound levels at the shooters ear. The trick is to balance the ejection port sound level with the muzzle sound level, sampled at the shooter's ear.
    Thank you for the reply. I appreciate the info and while I am aware of the function issues that arise from backpressure, I think I failed to articulate my question sufficiently. It's not my intent to turn this into a piston vs DI thread, but I would like to expound a little further on the subject of ejection port noise. So let's say we run a suppressor on a host weapon that's optimized from the start for suppressor use. Add to that a suppressor that imparts little or no backpressure to the system such as the OSS offerings. There's still gas being vented from different locations on each platform just as they would when being run unsuppressed. It's been said the gas vented from the gas block on older generation HK416's was quite loud, even when suppressors designed specifically around that platform were used. My experiences with the HK over the last decade were consistent with this. Not that noise from the gas vented at the block was any more perceivable to me over a DI weapon, but that the rifle was loud even with a suppressor.

    So if the gases being vented at the gas block on the HK416 contribute to it being a louder host weapon for suppressors and higher decibel readings at the muzzle, does a DI weapon not exhibit the same issue when gases are vented at the ejection port? My work setup is an 11.5" DI with SF can if that's any indication where my preference is at the moment. However, I do think the subject is worth exploring a bit.


    Tspeis
    Last edited by Tspeis; 09-17-18 at 22:36.

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    The 416 was a poor suppressor host because it was severely over gassed when using a suppressor. This resulted in additional ejection port noise and gas coming from the barrel back into the receiver, and your face.

    The gas that vents from the gas block has minimal effect on the sound pressure levels at your ear, at least compared to muzzle and ejection port noise.

    10" barrel rifles are loud, even with a suppressor, unless you're shooting subsonic ammo (and have an appropriate suppressor to go with it).
    Last edited by Slippers; 09-17-18 at 23:35.
    Will - Owner of Arisaka LLC - http://www.arisakadefense.com

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    Thanks for clarifying. I am familiar with the overgassing, but was unsure how significant the gas venting at the block was in terms of noise signature. I was led to believe it was significant enough to cause a slight increase in decibels at the muzzle when compared to DI guns of the same barrel length, which made me wonder if the same applied to DI guns venting at the ejection port. I found your info on WHY the noise at the ejection port (early unlocking) was happening to be helpful. Thanks again.


    Tspeis

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    From what Ive read, gasses coming out of pistons is higher pressure and louder.
    DI guns, the gas venting is quieter, but right next to your ear, so its “louder to you”. That said, my rifles are moderately gassed (not supressor only ports, some would consider them “over gassed”) but I dont notice much port pop. In fact, my friend said his weak side ear heard more (1 shot no ear pro).

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    I've found that port snap is somewhat unpredictable. I had the sweetest cycling adjustable gas block 11.5" which wasn't gassy at all. But the port snap ate my ass alive. I couldn't shoot it without ear pro.

    Under no circumstances would I ever own a piston AR. There's just no place for the nonsense.
    "What would a $2,000 Geissele Super Duty do that a $500 PSA door buster on Black Friday couldn't do?" - Stopsign32v

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    The only suppressed at I shot was a KAC 14.5 with their QD can in it. It was bad at all and made me want to throw my Omega on mine.

    A 11.5 with reduced gas port barrel and adjustable gas block is in my future. Well see how bad it is.




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    Some piston guns don’t vent (vent out the barrel), like early 10.4 Hk 416s or Adams Arms (no port pop). Some use more restrictive inlet ports to reduce the gas pushing on the piston vs unsuppressed setting (moderate pop) like the later 416 AGBs. Some vent by enlarging the vent to atmosphere, again to reduce the gas pushing on the piston, vs unsuppressed (loudest for port pop), like the Aug.

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    Yes--- but it's not apples to apples. Higher backpressure suppressors can make an AR run more aggressively, earlier unlock, louder port noise to the shooter. But, it can also mean more quiet at the muzzle... so there's a balancing act.

    The issue is you've got things moving faster than they should be, not that you have a higher back-pressure suppressor on there. It's like running downhill... if you fall on your face, it's because you were running too fast. You didn't fall because it was a hill. The solution is to not run as fast, not entirely avoid going downhill. (True to an extent, we're talking a hill, not walking off a cliff.)

    It's greatly over simplifying things... but you can get a more quiet suppressor at the muzzle to be more quiet overall than a suppressor that's quiet to the shooter, and louder at the muzzle. It may just require tuning the gun to run with that specific suppressor on.

    The importance of lower backpressure cans really comes into play when you CAN'T tune the rifle. (work guns, etc)

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