Dumb Gun “Knowledge”

 

1. Yes, I know. I cheated.

   Assuming a less than perfect vacuum (50%), the real silencer volume necessary is really only a cylinder 5” in internal diameter by 10” long, not allowing for the volume taken up by the baffle plates. With a perfect vacuum you can use a 10” cylinder 4” in diameter. Either one is actually usable, but without having the sealed depressurized chamber such a device is not going to get the blast down to much less than 120dB no matter how long it is or how many baffle plates it has. Studies have shown this and you can find them online.

   These things are legal in most of the world, except here in America the Land of the Free ... because our lawmakers are basically stupid and have bought the Hollywood lie.

   Now, do I have a seriously knowledgeable firearms person, engineer, or physics type who can point out my glaring error? Let me give you 2 hints: if the gun used has a 10” long barrel instead of the 5” one I used in the example, then I only need a vacuum chamber 2.5” in diameter, assuming I have a perfect vacuum in it. The longer the barrel is, the less silencing necessary. And PV=NRT.

   So I plead guilty to exaggeration, but my basic points are both still valid: suppressors can never be close to silent unless they use a vacuum chamber, and the dinky little things Hollywood shows us need to be many times larger.

   Posted by Drew458       04/07/2011  at  10:37 AM  



2. "Unfortunately heavy bullets at really low velocities aren’t usually fully stabilized, so accuracy suffers. Bottom line is that a truly silent firearm isn’t going to be accurate enough or powerful enough to get the job done at any kind of realistic range.”

   Ahem.

   http://300aacblackout.com/
   http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2085833
   http://www.thefirearmblog.com/blog/2011/01/21/aac-super-cool-suppressed-rifle/
   http://www.aacblog.com/?p=9440

   http://quarterbore.com/300whisper/sskwhisper.html

   The VSS Vintorez ("Threadcutter"”
   http://world.guns.ru/sniper/sniper-rifles/rus/vss-e.html
   https://secure.wikimedia.org/wikipedia/en/wiki/9x39mm

   This is not just a recent development nor is it limited just rifle cartridges.  In the testing of the Delisle suppressed carbine, circa WWII, .45 ACP, one officer. before witnesses, shot the head off of a duck swimming on a nearby lake at 700 yards.  The Germans had also developed a dedicated suppressed custom scoped bolt-action bull-pup, in 9x19mm, similar to the Delisle called the model GSDK; Gestapo SchällDamper Karabiner.  Made by Sauer & Sohn of Suhl.

   https://secure.wikimedia.org/wikipedia/en/wiki/De_Lisle_carbine
   (Note the double-set triggers)

   As for power?  A 240 grain Sierra Match-King, launched at a m.v. of 980 fps, loses about 100 fps per 100 meters of travel and has more energy at 100 meters than a .44 magnum does at the muzzle.

   So.  Heavy subsonic rounds.  Trajectory like a rainbow? Yes.  Unstable?  No.  Lacking power?  No.  Inaccurate?  Definitely not.

   Posted by P. Beck       04/07/2011  at  12:09 PM  



3. ”...one officer. before witnesses, shot the head off of a duck swimming on a nearby lake at 700 yards.”

   200 yards.

   Fat-fingered it.  Dammit.

   Posted by P. Beck       04/07/2011  at  12:49 PM  



4. Wait one damn minute. I seem to remember us having a discussion about that article and I sent you a link at the time.
   So, should I see my therapist and have my dosage increased Drew?
   I really thought I had these episodes under control but maybe things changed.
   Just askin,,

   Posted by Rich K       04/07/2011  at  10:33 PM  



5. Good responses!

   Rich, yeah, you may have mentioned something like this at one point. I get so many emails from you that some of them get lost in the shuffle. Keep it up!

   P. Beck - excellent. There is much to talk about with what you wrote.  I was hoping someone would bring up the 300 Whisper and other historical efforts towards a silent firearm. I was thinking more in the “wiper” school of silencer design though, since the design I threw out, with it’s 2 membranes, is indeed only a variation on the wiper concept. As for the rest of it, and the real reason I said that I cheated, see the overleaf on the post, below the “continue reading” button.

   Posted by Drew458       04/08/2011  at  08:35 AM  



6. Wipes haven’t been necessary for years.  The most advanced suppressor designs that are now available are more than a simple stack of “M” or “K” baffles.  That basic design goes all the way back to Hiram Maxim.  The latest designs are more “energy management devices”, that deal with the muzzle blast, flash and sound as signal energy to be re-directed and transformed rather than simply contained.

   For instance, if you treat the sound energy as a signal, transmitted over time, you can take the first half of the signal, bounce it off the front end of the can, reflecting it back on the second half, and the waves, being of the same frequency, would meet in the middle, canceling each other out.  There is no free lunch however.  Since energy is neither created nor destroyed but only changes form, the sound energy is converted to heat, so the suppressor must be constructed of high temp materials, because it’s gonna get god-almighty hot.  The gases are spun by the baffles, exiting as a swirl, rather than a straight jet.

   So you don’t need a large enough device to contain the entire volume of the gases, just strip the signal and execute a little volumetric “judo” on them.

   You now see a lot more suppressors being used in sniping for instance.  This is not just because of the desire to remain concealed.  Modern sound suppressors also have a positive effect on long-range accuracy.  On firing, the air in the bore is compressed in front of the bullet and exits the muzzle as a vortex.  This creates a wall of “dirty air” that the bullet has to pass through as it exits the muzzle.  This effects velocity, energy and induces yaw, all of which are bad for accuracy.  The suppressor doesn’t differentiate between air being pushed in front of the bullet, and the hot powder gases behind it.  To it, all gases are gases to be managed.  The suppressor on my SPR cut group sizes by half ( from about 1 m.o.a. to about 0.5 m.o.a.) just by virtue of the fact that it reduced the “dirty air” in front of the muzzle and reduced yaw just one extra fraction of a smidgen.

   Posted by P. Beck       04/08/2011  at  10:06 AM  

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