Therma-Tuff Suppressor Covers

 

A new addition to the Kaimai Suppressor range from D.F. Maisey Gunsmithing is their Therma-Tuff suppressor covers, which are rated up to 600 degrees C, and proving to be very durable. Made from braided fiberglass sleeving that is saturated with high-temp resins, it provides a breathable protective cover for your suppressor that will not burn, melt, or rot, and remains a snug fit on suppressors from 35-44mm diameter. They are far more durable than neoprene, and a lot lighter than rubber or silicone covers, and can be easily removed if required. Prices start from $20 for Compact (7-8”) suppressors. Any colour you like as long as it’s black!  For more info see the Kaimai suppressor website: www.silencer.net.nz  or www.gunsmith.co.nz . Also look out for updated suppressor tests in the future with our calibrated Bruel & Kjaer 2209 precision sound level meter.

 

       

Suppressor Sound Testing

 

Proper sound pressure level meters for testing gunshots are very expensive, and are not commonly available. The only sound level meters than can accurately and consistently measure gunshot peak sound pressure levels (in accordance with MIL-STD 1474D), must have a rise time of less than 20 micro-seconds (20uSec) and a sampling rate of 196,000 Hz or better (for digital meters).  The only meters that are still currently accepted in the industry for this purpose are the older analogue type meters such as the legendary Bruel & Kjaer 2209 (which reads up to 170dB) or the old Larson Davis 800D (which reads up to about 140dB, but  can be modified to go up to 160-170dB with add-on equipment). The only newer meters that meet the spec are the Bruel & Kjaer ‘PULSE’ system – which is a full laboratory-grade system that requires mains power to run (which limits it’s portability), or a similar system put out by National Instruments (though at the time of writing it is uncertain if that is still available or has been discontinued). These systems are VERY expensive to purchase, to set up and maintain, and often have annual licensing fees for the software as well.  These significant costs ($40K plus, and $10k per year for licensing) certainly limit their use and availability to the industry.

(Note: In 2017 a NZ-based outdoors magazine published a ‘review’ on a large number of rifle suppressors, and that testing used a single hand-held digital sound level meter – a Larson Davis LXT.  While being marketed as a sound meter that is supposed to be capable of measuring gunshots, this meter in fact does not meet the requirements of Mil-Std 1474D and is incapable of providing accurate, reliable, or consistent results for this purpose. This is largely due to the fact that it only has a rise time of 30uS at best (50% too slow) and a sample frequency of only 48,000 Hz (400% too slow). In recent years the Larson meter has been thoroughly discredited (by suppressor industry professionals) for use as a meter for accurate gunshot and suppressor testing.  This is undoubtedly a contributing factor to the errors and spurious results published in that NZ magazine article (and also some other YouTuber suppressor reviews using the Larson Davis LXT meter in the last couple of years.)  . The whole ‘review’ in the end could only be described politely as a complete shambles, and to go into the flaws and errors in that review would require a full article and investigation in itself. Particularly concerning was the fact that they were offered 2 separate mil-spec meters (by two of the invited suppressor companies) to run along side the Larson Davis meter, but refused to allow them. Why?? Or the fact that when some of the test results that they published were later proven to be inaccurate, they refused to publicly retract or amend/correct those results. Unbelievably,  instead of being apologetic the ‘reviewer’ actually made thinly vailed threats of legal action against anyone disputing the results or challenging his ‘good name’, where in actual fact some of the results they published as supposedly being accurate, were in some cases a misrepresentation and defamatory to those manufacturers, while in other cases the performance level of some suppressors was over-stated.  It is unfortunate that some people in the hunting and shooting industry are still using the results of these reviews tests as a reference or basis for comparisons between different brands of suppressors in the NZ market. Putting out bad data is worse than putting out no data at all, and flawed reviews with dodgy sound meters only do a disservice to the market, both for consumers, manufacturers, and re-sellers. Most hand-held sound level meters only have a peak rise time of 100uS at best, and phone-app for sound levels are even worse!  These sort of amateur sound test measurements are completely worthless, and misleading. Beware of being mis-informed by any suppressor reviews that are using cheap or uncertifed equipment that is not fit for purpose. )

IN ORDER TO PROVIDE ACCURATE AND TRUTHFUL TEST RESULTS (with an actual mil-spec sound meter) in 2019 we purchased and set-up a full laboritory-calibrated B&K 2209 system (along with B&K 4136 1/4″ pressure mic and field-calibrators) to be able to add accurate field-test data to our existing test data, and to be able to experiment and re-test with minor improvements or design changes. Later in the year we added another two late-model B&K2209 meters that have proven to be good, accurate meters as well, and allow us to experiment with taking readings from multiple locations for each shot (i.e. ‘Mil-spec muzzle’ left and right (1.6m high, 1m to the side at 90 degrees), and ‘at the ear’ measurements simultaneously).  And just now (March 2020) we have purchased a fourth late model B&K2209 meter to act as a back-up meter, or to measure sound pressure levels from a 4th location if required.  This will be the best set-up in New Zealand for sound suppressor and gunshot testing (up to 170dB), and will finally be available to provide accurate data for consumers or honest product reviewers who require it.