![]() (The only way to do this is to use faster burning powders.) I hypothesized that lighter charges would also reduce noise. I have experimented with other loads to see how light a powder charge I can use while still cycling my guns and producing the same muzzle velocity (about 1000fps) with the same 220gr bullet. The standard subsonic 300BLK load uses a 10.4gr charge of a relatively slow powder in order to provide enough gas volume to cycle a wide range of guns. The peak sound pressure levels were identical in each scenario. But as another test: I ran a wide range of subsonic loads through my 300BLK AR-15 with its standard gas system in place (i.e., autoloading), and then with its gas port completely blocked (i.e., locked breech). In fact, just attaching a suppressor to a centerfire autoloader that wasn’t designed for one can be such a nuisance that many designs and components now allow for the gas system to be adjusted. Similar mismatches can be produced with other actions. However, it is possible to tune these guns to this unusual round by using heavier bolts and/or springs to prevent the action from unlocking before the bullet has left the barrel. As a result, the case unplugs the breech before the bullet even leaves the muzzle! Since there is no suppressor on the breech, on the rifle this releases pressure of 128dB (vs 121dB from the muzzle with the breech locked) and on the pistol it produces 130dB (vs 127dB from the muzzle with the breech locked). Whether I let the actions cycle normally or held the bolts closed, the peak sound levels were the same, with one exception: 60gr Aguila ammo – which is very exceptional ammunition: Its bullet is 50% heavier than almost any other. 22LR pistol (the Buckmark) and 10/22 rifle ( Feddersen-barreled Ruger). Once we add a suppressor can the breech report exceed the muzzle report? It turns out that it can if a gun is poorly tuned, but that with typical guns and loads designed for them it does not. I.e., some of the same propellant that produces the muzzle report comes out of the breech. This usually occurs while the bore still contains a significant amount of propellant pressure. Modern autoloaders use gas pressure and/or momentum from the discharged round to eject the empty case and load a new one. A common question is whether a suppressed autoloading (i.e., semi-automatic) gun is louder than one with a locked action. Are Suppressors Effective on Autoloading Actions? ![]() The shorter barrel produced peak sound pressures 3-7dB higher than the longer barrel (depending on the powder load, as we will see below). I also ran a variety of subsonic 300BLK loads through two different AR-15s using the same suppressor (an AAC Cyclone): one gun with an 8″ barrel, the other with a 16″ barrel. 25″ for the rifle) the muzzle report is about 6dB higher from the pistol. Shooting the same loads through a rifle and a pistol (barrel length with AAC Element II suppressor 9″ vs. 22LR ammunition we can see something interesting: Barrel length has a significant effect on muzzle report. (Without a suppressor the same loads meter about 148dB.) Is Barrel Length Still a Factor with Suppressors? 22″ bullet leaving a suppressed rifle muzzle at just 1000fps, make peak sound levels that are roughly the same as manually cycling the bolt of the gun shooting them: about 120dB. We may further reduce the nuisance and noise associated with gunfire by shooting subsonic loads to avoid the loud and unmistakable sonic crack created by supersonic bullets in flight. Hence, we put suppressors on our guns to bring their peak noise down to “hearing-safe” levels. Virtually all firearms create pressure levels above 140dB, which is the limit established in MIL-STD-1474D to avoid unacceptable hearing damage. 22 round, but certainly louder than a suppressed round that travels 800 fps.This post follows the introduction to shots, pops, and sound pressure levels. Through a suppressed rifle, it's definitely quieter than a standard. I know this speed limit is variable according to temperature, humidity, and distance from sea level, but I can't seem to find out if 800 feet above sea level makes a 1100 fps round sonic or subsonic.Īn obvious answer is to just go shoot it. This avoids the supersonic shockwave or "crack" of a supersonic bullet, which, particularly for suppressed firearms, influences the loudness of the shot." () "Subsonic ammunition is ammunition designed to operate at speeds below the speed of sound, which at standard conditions is 1,126 ft/s. One of the boxes, not labeled "subsonic" had a speed of 1100 fps. 22 subsonic brands yesterday to shoot and compare.
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