well, if you are richer than croesus, you simply go to the surefire website, and order up a surefire integrated flash hider and suppressor, of the appropriate caliber and size, plunk about $2200 on the table, and forget about reading the rest of this.
it is about that simple.
you don’t have $2200 to spend on less than a pound of metal? read on, mcduff.
i have a friend of an engineering frame of mind, and he and i in discussing this, discovered that we both think spending this kind of money for such a simple machine is absolutely fucking ridiculous. on a per pound basis, this makes a mercedes sedan about a $10 million automobile. now, given the basic fact that a noise suppressor "does" absolutely nothing as a bullet and propellant pass through it, and is basically butt wipe simple in engineering terms, when in comparison a mercedes has its share of very exotic engineering refinements, precisely machined steel and aluminum parts, and computers that do everything possible to keep the car on the road no matter how big a dolt the driver is, or how badly he or she drives, ... , well then, to pay that sort of money for a suppressor is silly. the magnitude of the silly was described immediately above as "absolutely fucking ridiculous," and i have not run across any reasons to change my mind as i think about it.
update re: surefire: i poked a little fun at them when i wrote this. they make good stuff, but to me, they are sorta approaching unctuous when they talk about how good their product it. so, i decided to give you their link, because they do make a good product and they have interesting films of rifles and such firing in full auto with suppressors: as to pricing, the opinion remains firm at this page, that the prices are "absolutely fucking ridiculous." fun. http://www.surefire.com/Suppressors . interesting. all that, but priced beyond all reason.
and, i will tell you something else, which you are free to consider.
i would regard that sort of tactical use of a suppressor as having been precipitated by a very major blunder in tactics, field maneuver, situational awareness or however you would like to characterize it. as stated many times in these pages, i am not interested in gun fights, ... , you can get killed in a gun fight. i am interested in shooting.
"the det, don and ron doctrine." i got a note from friend randy ron in response to this article, chiding me for wasting time on what is obvious, and suggesting i just buy a good suppressor. in the course of his comments, he mentioned friend det & don, and commented on their mutual doctrinal belief that one shot is enough, and then get gone: no need to be attracting attention to ones self, by a lot of frivolous messing around. so, in honor of det, don and ron, i am suggesting that the proper use of a suppressor is to, ... , "get it done, & run," e.g., make your one shot, and be immediately on the skedaddle before the opposition arrives. this is "the det, don and ron doctrine." pretty damned good advice. end update re: surefire.
now, some of the hoity toity suppressor manufacturer's get downright huffy about how sophisticated their gear is as against the cheaper stuff, and say that what they do is measurable & predictable science as opposed to the amateurish guess work engaged in by their competitors.
to which i say, horse poop.--
now my favorite ar-15 upper shoots a 6.8mm (.277 caliber) remington spc, and quite accurately, when i use my best load of 28.2 grains of h-322 behind a 115 sierra matchking bullet, loaded to function reliably in my ar-15 magazines. how did i develop the load. well, i went to the hodgdon's internet website, got the load, and worked up to it gradually making sure i didn't blow off any fingers. i get 2550 fps at the muzzle on that load, which is good enough for me.
it shoots wonderfully, at less than a minute of angle from 100 to 400 yards. i am as happy as a pig in poop about that. now, contrast these results to all the other loads i tried before, using quality powers such as reloader 15, hodgdon’s h-335 and imr 4198 & 4895, which shot about “minute of grapefruit.”
why? i don't know. and, i defy anyone to come up with a precise explanation of why it is/was so. but, it is/was so. and, the same nut behind the stock, doing the shooting.
and so it is with suppressors. surefire says they know what they are doing. i sincerely doubt it. consider this. my h-322 load shoots very cleanly, with very little powder residue in the action after shooting, a very clean barrel, and very little particulate out the muzzle in the muzzle blast: i know, i have fired the muzzle mere inches from a white paper backstop, and h-322 leaves no residue. it also makes very little muzzle flash, even at dusk with full power loads. now, h-335 and r-15 are very dirty in comparison, they throw the brass different places that the h-322 brass (indicating very different pressure levels at the gas port, and therefore very different pressure curve in the barrel to that point), and they throw the bullets to wildly disparate points of impact as compared to the h-322 loads (indicating very disparate barrel harmonics on the bullets exit at the muzzle, along with the different pressure curves.) these powders leave the bore and the action very dirty after cumulative shooting.
go back to the previous paragraph, and read the little asides in the parens again. now, what these little asides say, is that the gases exiting the barrel at the muzzle just behind the bullet behave differently, and are differently constituted, as between types of powders, burning rates, and methods of manufacture. the long and the short of it, is that the powder gases going out a barrel behind a bullet behave very differently from load to load, brand to brand of powder, and type of powder used, because the powders are made differently, from different types and combinations of chemicals. the flow of the gas, the particulate composition of it in terms of inert materials, the size of those unburned materials, and the pressure and flow of gases are all different, using differing powders. simple as that.
surefire knows how all these different things behave when they go through a suppressor? they say they do, but they don't, because they cannot. just fucking cuz. cuz its all different, that is why, and when it is all different, it flows differently, behaves differently, and react differently to the internal mechanical terrain of a noise suppressor. in short, they all make noise differently, because the patterns of pressures, flow, harmonics and allied phenomena, are different.
so, i say, that even in the best suppressor designs, a lot of it is hit or miss, and trial and error, and depends upon the loads fired through them, even in the same calibers: things such as bullet weight, powder, velocity, pressure and the nature of the gas flow are all gonna effect what sound comes out the barrel. and, the fact remains, that in suppressor brands, the noise attenuation of a specific round fired through almost anybody's suppressor, e.g., read that everybody's suppressor, whether or not they know anything about what they are doing in surefire's opinion, is about 40 to 45 decibels in sound energy.
so much for science, engineering, metallurgy, materials and manufacturing expertise in making suppressor. if you want some empirical proof of what i say, go to pages 58 through 66 (with interruption for ads) of the may 2, 2011 edition of shotgun news, for an article by marco vorobiev, a former spetsnaz soldier, entitled "guns of the spetsnaz: part iv, pistols" and look at the photos on page 62 of the internals of a noise suppressor on a pistol designed by the ruskies for the spetsnaz. (designed from the ground up to be a “suppressed” firearm to be used by the spetsnaz in clandestine assassinations: it looks, for all the world, like a beretta or a p-38 walther with a big tube where the barrel ought to be.) the damned thing looks like a ron popeil, that’s “ronco” to you, vega-matic veggie chopper/cheese grater infomercial infamy: popeil once marketed spray paint to “hide” balding hair. and, a cheaply made one at that. and, i can gaurantee you one thing: the soviets didn't spend $2200 per pistol making the damned thing, but it apparently is worked, and worked just fine. again, so much for science, engineering, metallurgy, materials adn manufacturing expertise in making a suppressor: you could rattle a 9/16's" drill bit down the middle of the russian pistol suppressor, with room to rattle it.
so, my friend and i have been discussing ways to make an effective suppressor for a high powered rifle round, and do it inexpensively. (now, go back to a recent article appearing in these pages, entitled “… further noise attenuation for an already quiet round,” and read all the various advisements and cautions about delving into these mysteries, and dealing with your friendly revenuers at the bureau of alcohol, tobacco and firearms, and their regulations devolving from the national firearms acts. in short, if you don’t comply with the law involved, state and federal, in making this stuff, you are going to federal prison, some idiot federal prosecutor gets a hard on for you.)
and, as you might surmise, we hold the $2200 price point for suppressors in utter contempt.
how do you silence a high powered rifle round?
well, as it turns out, you do not. and, as a matter of fact, you cannot. even if you could remove all the muzzle blast from a rifle shot caused by the propellant gases exiting the muzzle, you cannot silence the sonic boom that a rifle bullet traveling faster than the speed of sound makes when the bullet leaves the muzzle: the speed of sound at sea level, one atmosphere at 70-degree fahrenheit, is around 1050-1070 fps. since a very high velocity round might be going upwards of 3500 fps at the muzzle in a varmit round, to say 2550 fps to 2650 in a 7.62x51mm nato round (.308 winchester) in a moderate velocity load, it is comfortably supersonic, and is going to make a sonic boom along its path, just like a jet fighter. it cannot be eliminated. period.
you see/hear it in the movies, as a “crack.” can the sonic boom be mitigated? sure, just make the bullet travel at less than 1050 fps, and no sonic boom. easy, eh?
so, we have the sonic boom in a high powered rifle round. and, we have a muzzle blast of around 180 decibels plus associated with the propellant gases leaving the muzzle, which will hurt you ears, and will excite considerable attention if fired in an inappropriate place under inappropriate circumstances, which may vary from locale to locale, person to person, and given the attitudes & concerns of those in those locales, and depending on whether one is the shooter or the shootee, so to speak.
the best of suppressors, and oddly enough, the worst of suppressors, if we are to believe the advertising copy and literature on the matter, reduce this muzzle blast/sound signature, by about 40 to 45 decibels, which is very appreciable. but, the sound is not silenced.
how do you, however, do it, that is, how do you attenuate or “suppress” the sound of a rifle shot? in short, and very simply, you enclose part of the flight of the bullet after it leaves the barrel in a chamber or vessel in which the propellant gases are allowed to expand and cool before they reach the open atmosphere, thereby reducing the violence of their expansion when they do so, and perhaps continued combustion of propellant not burned in the barrel. (no, surefire cannot account for that in every load, now can they? no, they cannot? so, they have not planned and engineered for every contingent difference is the propellant gases going through their suppressors, have they? no, they have not. so they don’t know everything, do they? no, they do not. and, as a matter of fact, neither do i, and what i know is way less than what they know. i just know that $2200 for a noise suppressor is “absolutely fucking ridiculous.”)
now, can you do this just by adding on a simple tube to the end of the barrel, with no gadgets in it? why, yes you can, and it would work, and it would be very long and heavy, and quite cumbersome. but, it would work, simply by “simulating” the open atmosphere until pressure and temperature fell away to the ambient.
so, how do you make the tube shorter and less cumbersome, but, still effective?
well, you sort of do it in the very same way that bose electronics makes a large bass signature in its stereo equipment package in very little boxes. and, the same way you make a coronet out of a long herald’s trumpet. (same things you know, without the valving: and what do valves do? why, they simply supply different lengths for the sound to travel, before it reaches the end of the tube. translating, by the way, a “fwewahhhbbb” sound into clarion ringing notes. sound familiar?) now, you cannot twist a noise suppressor into a coronet shape, because the bullet following the laws of inertia, being set in motion in a certain direction and velocity wants to continue in that path at that speed, (“wants” very badly, in a mechanical sort of way) and, if shot in space without atmosphere and the effects of gravity, would. anything impedes the dictates of inertia is going to suffer for it, as the bullet is going on its path right through obstacles thrown in its way.
but, in effect, you do acoustically & mechanically to the propellant gas plume after it leaves the muzzle, just what the bose speaker and the coronet do to the air & energy flowing through them: you change its properties by altering its energy state.
in a “suppressor,” you induce the propellant gas to follow a longer and slower path to the atmosphere, by giving it a chance to behave as it “will,” e.g., following simple laws of mechanics and physics. you offer the propellant gases, under tremendous pressures, the chance to enter larger volumes, in other words, you offer it a path into chambers inside the suppressor. looking for the path of least resistance, just like flowing water, the propellant gases follow ports and passages into dead end chambers where the temperature and pressure are less, diverting their path from direct exit from the muzzle and suppressor. having got into these chambers, the gases want out as they are when pressure and temperature again rise, and they again follow exits seeking the one atmosphere of pressure of the open atmosphere, as opposed to the 10,000 psi or so that they are under at the muzzle. it is very much akin to an extremely quick ebb and flow of waves against the shore, as pressure, temperature and energy surge to flow to infinite equilibrium. sort of poetic, isn’t it. but, nature seeks equilibrium, and even a very quick and temporary exploitation of this fact can alter physical forces very significantly: this reduction in noise signature of a muzzle blast/flash takes place in slightly less than 1/1,000’s of a second, more or less.
it takes some additional time, therefore, for the propellant gases to get out to the open atmosphere, during which the duration of the exit of their entire volume is elongated, and during which their sum total of energy is attenuated by a drop in both pressure and temperature, from exposure to increased metal surfaces which absorb their temperature & from the increased duration of their exposure to increased areas of volume provided by the suppressor’s interior cavities.
it is the manipulation of time in which to do work, the classic definition of mechanical advantage.
the longer the tube, and concomitantly the greater its baffled/coned volume, the more efficient the noise attenuation process. the shorter the tube, the less efficient the process, but the greater convenience of the machine in terms of size and weight. in short, you diddle for an added compromise in terms of convenience and size of the machine versus noise attenuation. this compromise, and engineering skill, is expressed in terms of the size & weight of the suppressor need to get 40 to 45 decibels of energy out of the muzzle blast.
now, you can google this subject, and as per usual wikipedia has a good article, and other clubs exist which discuss the various features of suppressor construction, as they have developed. suffice it to say, cones of various shapes, sizes and passage openings have replaced the simple baffle as favored designs, and the designers also tout the advantages of designs with scavenge debri from building up in the suppressor, by allowing them passage from the suppressors chambers.
when you think about it, the design of this evacuation process is pretty simple. if you are doing everything you can to low the pressure and temperature of a highly dynamic gas, you are attempting to absorb energy from it, … , you make it expend energy to get out of your device. well, if you are at all successful, where is the debris in the form of metal shavings, metal particles, soot and unburned powder granules gonna go? they are going to drop out of the propellant stream, and into the bottoms of the suppressors, into what i call the scuppers of the device. like everything else in this situation, they settle to the bottom. so, what the designers do is make holes in the bottom of the suppressor baffles and cones for this gunk to pass through, and out of the device. well, you make too many holes of two large a size offering to straight and uninterrupted a passage for the gas to go through the suppressor, then the suppressor is not gonna work very well. (hey, surefire, you got every contingency of this worked out? laughing. no, of course surefire doesn’t, because it hasn’t anticipated every conceivable way or manner in which every conceivable propellant carries all this stuff along. they cannot, is my obvious position in the matter.)
so, having said all this, how would my engineering friend and i make a suppressor?
well, we would start with simple metal.-- such metal will be inexpensive, common & readily obtainable, and easy to form using rudimentary processes and machines. steels are an obvious natural, and 10 to 11 gauge steel ought to be strong enough & readily plentiful. at this juncture, my engineer friend turns to his materials manuals, and looks to the yield and burst strengths of the various sheet metal thicknesses, and confirms or negates my eyeball appraisals as to sufficient strength.
then we form it. for the baffles, my engineering friend think that cones formed in a simple hydraulic press should be able to form the internal pretty easily, simply by pressing them in metal dies of the appropriate shape. oddly enough, a hydraulic jack placed in a sturdy metal frame, with a male and female die, and a disc of metal, will do this pretty easily: you don’t need a stamping mill the size to do an auto body fender. then you have to get the formed shape out of the dies, which i would suspect would be the hard part.
how about a metal tube to put it all in. well, we can turn to an exhaust pipe store, like midas, if we like. but, the stuff used there is thick walled, very heavy, and way stronger than a vessel needed to contain propellant gases for 1 to 2 thousandths of a second. it is too thick, stout and heavy for what is needed.
i would favor sheet metal, placed into a revolving mandrel, turned and drawn around a simple bar placed close to the mandrel, so as to form the sheet metal to the mandrel. bring it around full circle, tack weld it, and then remove to a fixture where it could be welding.
weld.
thread both ends. fill it full with baffles, discs and cones to your heart’s desire, of any shape and configuration which seems to you will cause a propellant stream to seek chambers of greater volume and lower pressure than they are in, and will cause delay in the propellant stream from reaching the open atmosphere. use the insight to design gained in the aeronautical industry: is it looks good, it probably is good. worked for the spitfire and the mustang, works for the corvette. hey, it is no more difficult than that, no more complicated. put in a little passage way at the bottom of the whole mess to scavenge the particulate matter that drops to the bottom of the suppressor.
thread one cap to go on the standard threads machined at the end of ar-15 barrels for flash hiders. thread on the other cap, with a hole in the end of it large enough to let the intended projectile pass. now, the guys who sell you the top end stuff will insist that this “fit” has to be super precise: they brag about making the hole for passage down the middle of the “suppressor” being 3 or 4 thousandths over the diameter of the bullet, for instance. o.k. by me, it’s your money. personally, i doubt it makes a real big difference. by the time the stuff gets to that juncture, and the bullet is out of its way as an impediment to getting out the suppressor, the hole is a hole, and if it is .3085 or .310”’s in diameter, i doubt it matters much. and, i doubt very much that it makes significant difference at the passages in the baffles and cones, either: there’s gonna be some blow by, regardless, and the differences in volume of the blow by probably are not that big a deal.
now, you want to have enough skill at this so that the baffles and cones and such don’t rattle around loose inside the steel tube, because if a bullet strikes them at 2600 feet per second it is gonna damage things, and probably tear the hell out of the suppressor, and it probably ain’t gonna do the end of your rifle’s barrel much good, either.
so, you’ve got to figure a way to index the cones & baffles, and you have to figure a way to keep everything on axis, so that the baffles and cones don’t tilt, and rattle around.
but, this is not insurmountable. witness the russian pistol referred to above. pre-drill some holes in the tube. have a fixture to hold things plumb, true and on axis. spot weld ‘em in. have spacers, or gasp, figure out just how many of the damned things you can put it, hey, the more the merrier, to fill the thing all the way to the ends, so that the caps screw on tightly. it can be done.
say you get done, and you test fire your legal suppressor in a state where you can use the damn things legally, with some acoustical equipment that measures sound energy, this test firing to take place next to a rifles in your caliber with your load, one with a surefire suppressor costing $2200, and one with your less than $2200 suppressor.
say the “store bought” surefire measures 120 decibels, and your suppressor measures 121 decibels. what, you are gonna go home and blow your brains out, right? laughing.
now, in discussing the internals with my friend of the engineering interests, i propose used automobile exhaust values, for their air flow characteristics, and cheapness and anticipated availability. just machine holes in them right, and toss ‘em in. my friend said, hey, that’s stupid. o.k., it’s stupid. they are heavy, and imagine hard to machine.
but, don’t be afraid to be stupid if stuff gets scarce. have a fallback position.
one final observation.
in the operation for the invasion of france in what is now called the “d-day invasion,” the english devised clever floating docks by which men and material could be brought ashore when the beached was secure. float ‘em up to the shore, and put together, and you had instant docks. well, the english channel off the coast of normandy is stormy, and the english anticipated storms, correctly, and devised breakwaters to break the force, and the rhythm, of the storm waves against the docks.
they worked marvelously. and, to make a point, in design and fabrication they were butt wipe simple. they were plates with holes in them. the holes forced the energy and water of the wave motion to alter path, and to alter (slow) velocity and to drop energy from the kinetic motion of the wave, and from the wave energy in the wave moving ashore. it didn’t stop waves, thank you king knute for the object lesson, but it prolonged their moment, slowed them, and dropped the water from the wave, so to speak.
sound familiar? it should, if i have done my job and if you have read attentively.
the key here, in terms of designing your “break water” baffles and cones for your internals, is that you made irregular sized holes in your baffles/cones & in different locations for the propellant gases to flow through and over, and that you space the baffles/cones so that the holes do not line up on axis, and so that no regular pattern develops in their location such as might induce the buildup of harmonics inside the suppressor. you want to induce turbulence and chaos and “confusion” in the path of the propellant, by alternating restricting and confining its path and then opening the wide vistas of cavernous spaces before it. in short, we induce inefficiency into the path of the propellant to the low pressure of the open atmosphere, and slow it, and leave it muddled.-- we don’t want, for instance, to replace the muzzle blast at 180 decibels with the trumpet blast of e-flat at 120 to 140 decibels, now, do we.
different sizes. different locations. no straight paths. induce the long way out. make it look like leonardo davinci’s depiction of high winds and waves. that’s the goal.
and, remember the immortal lyrics of doctor john if it doesn’t work perfectly the first time. “just do it wrong, until you do it right.” and, when asked, just say that you engineered it right, the first time. who the hell is gonna know the difference, besides you wife and your dog, and you long suffering neighbors.
i won’t tell, if you don’t.
john jay @ 04.22.2011
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