Taking Care of Your Sound Tech Millennium Can (2004)

Soundtechsilencers.com [email protected] (205) 664-5860

Materials, Coatings, Tightness & Overheating -- The screw-on M-Cans in .17 HMR, .22 LR, 7.62x39mm, .223, .308, 9mm & .50 BMG have been our strongest selling products. The centerfire cans are only available in chrome moly, which has great strength and more heat resistance than stainless steel. The cans are meant to be used, and will take moderate knocks and abuse in stride. The .223 cans are most commonly abused by novices firing on full-auto. They will heat up quickly and can be damaged by a careless or unthinking individual. A single 30-round magazine will cause no problem. Several 30-round magazines fired back-to-back on full-auto will burn the coating off the center of the can, and could make it red hot (about 1,000 degrees F). When the can reaches about 1,400 degrees it will probably deform from internal gas pressure at that plastic state. Since standard AR15/M16 threads are small and right-handed, the can may tend to unscrew from the barrel. Since the metal gets so hot so quickly, few will bother to touch it to make sure it hasn’t become unscrewed. All screw-on cans must be kept tight against the shoulder on the barrel in order to remain in alignment! Once any can unscrews (even a little) it will tend to droop, and this makes it vulnerable to baffle strike. Larger, relatively fine threads that oppose the direction of rifling are superior in this regard, but few want to change existing threads on their weapons. The bottom line – if you must fire a .223 on full-auto, do so in short bursts, and don’t overdo it! Check to see that the can stays tight against the shoulder of the barrel. The M16 will get so hot that rounds will fire by themselves (cook-off) after about 140 rounds of full-auto fire. The barrel and bolt will be ruined at this point. It is possible to totally destroy most of an M16 in less than a minute with full-auto fire. Think about what you are doing! If the coating starts to burn off the surface of the can, stop firing, and let the entire system cool down!

The .22 rimfire cans are available in both stainless and a black, powder-coated, 4130 chrome moly steel. Stainless steel cans may be re-polished or bead blasted to remove nicks and cosmetic blemishes. Black cans may be lightly sanded and recoated. Painting has a significant advantage over bluing or Parkerizing, since it is easily renewed, and can be quickly camouflaged to match one’s surroundings. We use a commercial bake-on coating which may be lightly resanded and redone if and when cosmetics are a concern. New coating materials continue to come out, and we will periodically switch to a better coating if one comes to our attention. Parkerizing is recommended for cans that will take a great deal of abuse, and we can furnish this coating at an additional charge.

Maintenance -- In .22 LR there is little maintenance to do beyond shooting and then locking the action open to allow accumulated moisture to vent out. Since powdered lead and grease from the bullet lubricant builds up in the rear end of the can, this tends to protect against corrosion to some degree, as long as moisture is allowed to evaporate. Accumulated powder residue will occasionally catch fire and burn. This is no big deal. The cans are built from tough, welded, aircraft-quality steel. The fire should burn itself out within six seconds. There is no need to remove a .22 can from its host weapon unless you want to mount it on another weapon. The Monolith cans are permanently mounted (welded) to their host weapons’ barrels. If they absolutely must be removed the easiest way to do this is to cut the barrel off behind the can and bore it out of the suppressor on a lathe. Cans built for the .223 are very effective on .22 LR caliber weapons. Cans built for .22 LR CANNOT be used on .223 caliber weapons, since the internals are not designed to take the far more intense blast and strain. If you want a single can that does it all, go for the .223 can, which also works on .22, .243 and 6mm rifles. The .223 and .308 cans are relatively self-cleaning, since high pressure gas blows most crud out. The centerfire cans will normally not require much in the way of cleaning, however they will pick up a considerable amount of water in the form of condensate. If this water is not encouraged to evaporate after a shooting session it will not go away, and may rust the inside of a rifle’s bore if the can remains on the weapon. Nitric and sulfuric acid were used in the manufacture of smokeless gunpowders, and not all of these are washed away before the powders are sold. If water stays in the bore the residues of these acids will recombine with the water, making a solution that will rust the inside of both stainless and regular carbon steel rifle bores, usually more near the muzzle than near the breech.

Store Your Weapon in a Muzzle-Down Position! – Again, suppressors capture a lot more than sound. They also capture a lot of water, filth and corruption. Powder residue and condensation will drop down the bore of the host weapon if it is stored in the traditional muzzle-up position. Always stand, position or hang the weapon so it is stored with the muzzle pointing down, with the end clear and the action open so that air can ventilate through the suppressor. Storing muzzle-up will soon clog the action, resulting in failures to feed or ignite. We are telling you this because a number of weapons have been returned to us because they failed to function. After we cleaned powder residue from the bolt face and inside the firing pin hole, the weapons were restored to normal operating condition. Residue clogging the firing pin hole is not always apparent or obvious. This is not rocket science. Let gravity be your friend. Always store suppressed weapons flat or pointing down to prevent trouble. Leave the action open or remove the can while hot to allow accumulated moisture to evaporate!

Flushing With Solvents and Protecting With Grease -- The M-Can series is massively overbuilt. The ends are solidly welded together and will not come apart. Cleaning is rarely required. When necessary it may be accomplished by dipping the can in a solvent (such as paint thinner) and draining. Blow the unit out with an air hose or fire a few rounds through it. Lately we have taken to using a little red jetlube grease or tapping wax/oil to lubricate suppressor threads that appear too tight. We also use a small amount of grease in the rear blast chamber of centerfire suppressors. This stops first-round-pop with subsonic ammo, and the grease gets deep into the recesses behind baffles, keeping rust at bay. Those recesses will either fill with water and corrosive particles, or with protective grease. Whichever gets there first will stay there the longest. The best way to apply grease inside the rear chamber is with a syringe with a bent tip, or with canned, foaming grease. Rotate the suppressor as the grease is applied. The grease should stick to the wall of the rear chamber or it could ball up in a mass in the bullet’s path. Don’t overdo it with the grease! Not much is required, and too much will cause problems with bullet flight and baffle strike. If a can shows a 36 dB reduction dry, it will often go to 46 dB reduction with a little grease in the rear chamber. This can be very useful in animal control situations in urban areas, where confrontations with animal rights activists are more likely. Water also works to reduce the sound level, but grease lasts a little longer, doesn’t cause corrosion problems, and typically stays put. Pistol cans with recoil boosters should be anointed with oil or grease in the rear expansion chamber to keep the piston and spring on the rear of the can lubricated and operating. The boostered cans do allow flawless cycling in semiautomatic pistols, but they also need to be kept lubricated in order to remain functional.

Why We Recommend Large Diameter Threads -- The M-Cans in .17, .223, 7.62x39, .308 and .50 BMG come with massive, single-point mounting systems, utilizing threads as heavy as barrel diameters will allow. The centerfire cans were redesigned and upgraded during 2003/4, and are now superior in dB reduction to most existing cans of equivalent size and weight currently on the market. Most of the military and commercial M16, .223 barrels are threaded for the standard ½-28 thread, commonly found on M16s. Whenever possible, we thread .223 M16 cans 11/16" or larger, LH. We feel that this thread size is superior because 11/16" threads are heavier than ½-28, and because they oppose the direction of twist on most rifling. Some flash hiders come with lock washers, or peel washers to time those flash hiders that have a solid bottom. Do not use lock washers in conjunction with a suppressor! Some washers will tilt the can away from the bore’s axis, allowing baffle strike! This should be obvious to most, but apparently it wasn’t, as we’ve had to file out cans that had bullet strikes on the front-end caps because some customers used a lock washer on a ½-28 thread. The fit of the barrel shoulder to can requires a proper metal-to-metal contact. Some lock washers (or bayonet lugs) make proper alignment impossible. The standard thread on the .50 BMG is 1-14, RH, which loosens as the host weapon is fired. We prefer a LH thread, and have standardized on 1-1/8-LH for the big .50, after consultation with a number of premier barrel makers. That said, we will thread your can to any thread that your existing barrel is set for.

LH suppressor threads self-tighten when bullets are fired in barrels with right-hand rifling, as a reaction to bullet torque. The threads may be loose as one turns the can on, but will tighten up and straighten out as the can snugs up against the shoulder on the barrel. The threads serve to center the can. Pressure against the shoulder keeps it straight. Keep the can firmly against the shoulder, but do not over-tighten! We believe that accuracy will be greatest when the muzzle of the weapon is as large in diameter as possible. Before suppressors came into vogue the only thing hung on the end of a barrel was a flash hider. Because the flash hider was short and small, the threads used to attach it were small. Prevailing thinking at the time was to keep the diameter of the hider as small as possible so that the appearance of the barrel contour would not be compromised. This is backward thinking! If a part like a muzzle brake, flash hider or a silencer is important enough to be included, it ought to have a size and proportion necessary to its function.

Suppressors are much longer and heavier than flash hiders, thus the threads that hold them have to be able to handle a very strong forward pull when each charge of high-pressure gas hits. One does not build a beam with a tiny joint in the center, but that is the way many people put joints between barrel and cans. Since suppressors are longer and bulkier, they are subjected to greater forces during carrying and handling. It is for these reasons that the joint between barrel and suppressor obviously requires high strength and larger diameter threads. A tree trunk is thickest near the ground, where leverage requires that it have the most strength. Learn from nature! A barrel should be thickest at the breech, and thick again where it joins a suppressor. One doesn’t put wheels on a pickup truck with 1/8" diameter bolts. Neither should one put a suppressor on a powerful centerfire rifle with a tiny, half-inch diameter thread. Our rule of thumb is to use the largest thread and shoulder size we possibly can, in order to give the greatest amount of strength and stability to the barrel/suppressor joint. Just because the U.S. Government has been using the tiny ½" thread for several years doesn’t mean that it was the right thing to do. While the M16 was in many ways a brilliant design, the government has managed to really mess it up with a number of short-barreled "improvements" in recent years.

Weld Appearance -- Since each end of each suppressor is jig welded in place, by hand, the welds may show some variation in surface profile. We could machine most of the weld off to give the appearance of perfection on the surface, but this would leave the actual welded joint weak. We choose instead to lightly clean up the surface with a file and sandpaper on a lathe. This often shows a few surface imperfections, but leaves the joint very strong. We hope that you will agree with our philosophy that strength and utility are more important than an unblemished appearance. Some of the welds are so perfect that we simply leave them as they are, without filing or sanding. By the same token, we will squeeze the baffles and spacers together under extremely high pressure before the last end cap is welded in place. Firing a .308 or .50 BMG rifle with a can will tend to compact all of the baffles in the stack (from the blast baffle on forward) from the powerful concussive forces. The tube actually stretches longitudinally as well, especially with the mighty .50 BMG. The blast baffle may rattle in some cases when the can is shaken. While it sometimes seems as though all the parts are moving back and forth an inch or more, in reality the movement is less than 1/32nd of an inch, and the rattle is usually confined to just the blast baffle. This is no big deal and is nothing to be concerned about. Eventually it will stop. Weapon accuracy and precise baffle alignment are not affected in any way.

Self-Loading Pistols -- Those who want suppressors for pistols with moving barrels should be aware that even a small increase of weight on the end of a pistol barrel can (and usually will) prevent the weapon from cycling properly. In most cases a suppressed pistol with a non-boostered can and a moving barrel will have to be cycled by hand. Any self-loading pistol will be louder than one with a firmly locked breech because high-pressure gas will come out the rear end before pressure in the can drops. Most .22 rimfire pistols have fixed barrels, and these cycle reliably with suppressors mounted. The Makarov in .380, the Heritage Arms Stealth in 9mm & .40 S&W, and the H&K P7 are the only centerfire pistols that will cycle reliably with cans on their muzzles. Unfortunately, the .380 tends to be fairly loud because of pressurized gas coming out of the rear end of a blowback pistol. Very few pistols were designed from ground zero to be suppressed. Recoil-operated pistols tend to be very fussy with regard to their cycling systems. The market for pocket pistol suppressors is very large, therefore a number of recoil-enhancing devices exist to aid weighted barrels in the cycling process. Most of these work fairly well when new and freshly greased, but they absolutely must be kept lubricated in order to remain functional. Our pistol suppressors tend to be of medium size and are fairly simple. We recommend the simple can and hand cycling whenever practical. The more complex boostered can is built for those who want flawless semiautomatic cycling, but again the booster piston has to remain lubricated in order to function. We do manufacture a lightweight aluminum can that works on some pistols without a recoil booster, but a lighter weight recoil spring has to be inserted, or the original spring has to be shortened. The Beretta 9mm FS is the most tolerant of subsonic ammunition, with a lightened spring.

Suppressed pistol fire should be subdued and restricted to a few shots at most, during covert operations. Hand cycling can be practiced, and this will result in a quieter, more covert operation than firing multiple rounds with abandon. Again, a small amount of grease, foaming grease, or water in the rear chamber of a suppressor will greatly enhance the quality of silence. The enhanced effect found with the use of an ablative material cannot be overemphasized. In most real situations one or two shots will be sufficient to accomplish an objective. If the objective is simply amusement, stick with the .22 LR in a Ruger MK II, the Beretta 21A or another favorite rimfire pistol.

Usually grease will allow from 10 to 20 centerfire pistol shots to be fired in relative silence, while water will provide about six shots. The use of subsonic ammunition is imperative for ultimate silence. Supersonic ammunition will not allow one to shoot without being noticed unless the target is closer than a few feet. We make tiny cans for the Beretta 21A pocket pistol, which is about the best of the tiny semi-autos. These are working very well, even though they do occlude the sights. Even here, a slightly larger can works better. The sights can still be used effectively with the imaging technique, where one aims the weapon at the target, imaging where bullet impact should occur. Threaded barrels usually come in many different lengths. Since many pistols use springs and guide rods with various lengths, it occasionally happens that the guide rod is too long, or the barrel is too short. Hand cycle the weapon by hand before use to ensure that the guide rod will not strike the rear of the can when the weapon is fired. We make can extensions of different length to accommodate barrels that are too short. Usually the extension has to be at least 3/8ths of an inch long. If your weapon requires a longer extension, please let us know about it before you damage a guide rod or slide.

High-Power Rifle Cans for Animal Control -- A number of clients have purchased cans for rifles in the .223, 6mm/.223, 6mm BR, .243, 7mm-08, 7.62x39mm and .308 class. In rural areas, high-velocity, supersonic ammunition can be used with fair effectiveness. A ballistic crack still exists, but it does not carry like an unsuppressed muzzle report will. For wildlife control a high-velocity, centerfire hunting round is superior to a .22 caliber round. A small 6mm bullet with an open tip, weighing from 85 to 95 grains and accelerated to roughly 3,000 fps, will be fairly effective on coons, larger cats, beaver, nutria, fox, deer, feral goats, etc. For feral hogs a heavier .30 caliber, 150-grain bullet is often required, since these animals carry a layer of protective armor that is fairly tough. In urban settings subsonic ammunition in a small cartridge is required, as it provides a much greater level of silence. Again, a bit of water or grease in the rear chamber of a suppressor will quell the phenomenon of first-round-pop, allowing an almost undetectable level of silence.

Much animal control takes place at night, when sound travels greater distances and most working people tend to be at home. In urban settings we recommend the use of a small amount of water, lubricating gel, KY, or foaming grease in the rear of a rifle-caliber suppressor. We have been using a Thompson Contender pistol with a 6" barrel, chambered in .38 special. Connected to this is a small 1.25 x 7" muzzle can, with a touch of grease in the rear chamber. With Blazer, 200 grain, soft lead wadcutters, this round (at roughly 800 fps) will penetrate from 9 to 10" of tissue, and expand to about double its diameter. If an instant subsonic stop is required, the heavier flat-nosed, hollow-based, soft lead, wadcutter bullets in .44, .45 and .50 caliber are even more effective. Over the years we have found that an instant stop is far more likely if a heavy, large-diameter, flat-nosed bullet stays within the primary target. In soft-skinned animals, 10 to 12" of penetration is close to ideal. Many of the soft lead Cowboy Action Loads provided by Black Hills Ammunition are subsonic, accurate and very effective. If instant stops are required, we again suggest a fast-moving .223 or 6mm round with a fairly light hunting bullet. A surprising number of professional game control people continue to use accurate .22 LR rifles for this type of work. They are typically experienced hands that know how to deliver carefully aimed shots that are perfectly delivered, and do not shoot unless they are absolutely sure of the outcome.

It is important that any subsonic shooting that takes place be very accurately directed, with head shots and a good working knowledge of anatomy being critical. The range should be between 20 and 50 yards and shots should be taken from a rest to ensure accurate delivery. Always be sure of a backstop and the likely direction that an exiting bullet will take in the event of bullet-skip or overpenetration. Don’t take the shot unless you are sure of the outcome. Again, do not use a military FMJ bullet that is too heavy, because doing so may promote overpenetration. We recommend that bullets be tested in jugs of water before taking to the field. If a bullet will penetrate 15 inches of water it will probably penetrate 10 inches of living tissue. If a bullet penetrates 48 inches of water it will probably penetrate 32 inches of living tissue, and a wildlife officer will have a stray bullet and a possible lawsuit to worry about in an urban environment. HJ Ballistic Research (256 447 1987) is one of a number of manufacturers who custom load subsonic rounds in some calibers. Always test velocity in your weapon to ensure that a load remains truly subsonic, with 975 fps being about right. Remember that shorter barrels (paradoxically) often shoot subsonic loads faster than longer barrels. Turning a bullet backwards before loading improves both accuracy and subsonic performance.

A proven .223 caliber round is Black Hills’ 60-grain soft point and the Hornady 65-grain TAP. These are supersonic rounds that probably will not overpenetrate a target, but they will carry a ballistic crack. A 60-grain ballistic tip bullet in a .22-250, or a 95-grain soft point in a 6mm BR cartridge are even more effective. Generally speaking, any medium-weight .308 full-power round designed for hunting will be effective in a rural setting. Subsonic .30 caliber rounds have been proven very difficult to design for large volume cartridges since they just won’t perform on body shots. The industry is working hard to come up with an effective round, but not doing well. The main problem is that most .30 caliber bullets are very hard and tough, thus they will not tumble, expand or open up at subsonic velocities. Initially, we leaned toward heavy bullets in the 200 to 260-grain range, but these were found to make very tiny, narrow wound channels and to overpenetrate badly, wasting most of their energy beyond the primary target. We are now leaning in the direction of smaller, lighter, softer bullets with open tips, designed to expand at modest velocities. While these carry less energy, they do tend to stay within a primary target and they do make a slightly larger wound channel.

A few individuals have made soft, long, heavy bullets of plain lead. If spun just fast enough to provide accurate delivery, these tend to bend in the middle shortly after entry, going through the center of a target sideways. Since expansion of a subsonic bullet is normally limited or non-existent, soft lead bullets that bend in the middle as they strike (and then continue sideways) provide the greatest likelihood of success in the subsonic .30 caliber field. While incredibly simple in theory, this has been a technological breakthrough that no manufacturer has yet to capitalize on. Soft lead bullets are almost always far more effective than jacketed bullets at subsonic velocities.

Wildlife control personnel in New Zealand have experimented with Ram Set, .22 caliber rimfire blanks inserted in the tips of drilled-out .44 Magnum bullets, driven at subsonic velocities. These must be loaded by hand into single-shot weapons. We are told that they initiate expansion sufficiently to be effective at subsonic velocities. Bad PR could result if these were used in a law enforcement situation. Normally, federal and state operations against nuisance wildlife in airports and rural settings are covert in nature, and do not attract attention. Be careful how you conduct an operation, and maintain a low profile. Look around. Be aware of who may be watching. Pull downed animals out of the area and dispose of them in a sensible manner. Give the carcasses to a processing facility and donate the meat to a prison or charity. If carcasses are left in a field the bones often break into sharp fragments that puncture implement tires. When in doubt, or if public attention appears to be directed towards you, have the common sense to break off the control operation and continue on another day at a different time.

Ammunition Suppliers -- There are several types and brands of ammunition that are well worth knowing about. If you have a rimfire weapon with a barrel longer than 4", most of the generic ammunition found at Wal-Mart will go supersonic, which means that it will deliver a loud ballistic crack when fired. The firm of Centurion imports and carries several varieties of subsonic rimfire ammunition. Their current toll-free phone number is 800-545-1542. Located in Texas, they will sell case lots to individuals. The order number for Black Hills Ammunition is 800-568-6625. Black Hills makes and distributes uncataloged 147-grain subsonic 9mm FMJ ammunition. This is a very versatile load that is subsonic out of both pistols and sub-machine guns. Black Hills also makes subsonic ammunition in .308. Success with subsonic ammunition is very dependent on lot and type, and if you are using this ammunition to harvest or remove animals it is very important that you test what you are buying or load your own. Continue testing until you have a product that will deliver, and stick with that. Know your anatomy, and study vital areas very closely.