A Custom Made Resistive Heater on my PCP REXIMEX Rifle

 A Custom Made Resistive Heater on my PCP Rifle

I want to talk about PV=nRT (the Ideal Gas Equation) and that basically, if you have forgotten your physics, to remind you that when some pressure vessel gets hot, the gas inside of it wants to expand and hence the pressure will rise in accordance with the temperature change and conversely, if the temperature gets colder the gas pressure will decrease within the vessel.

However since the volume of our cylinder doesn't change we actually need to derive another formula from the ideal gas equation.

From Joseph Louis Gay-Lussac 

P1/T1=P2/T2

Here we are comparing the same substance under two different conditions.

Where P1  and T1 are the following: initial pressure and initial temperature, and P2 and T2 are the final pressure and temperature.

Pressure is measured in Pa  (pascals)

1 bar=100 Kpa = 100,000 Pa

200 bar is then = to 200X 100,000= 20,000,000 (Pa) ie 20 Mpa

or 2 e7 Pa.

Temperature is measured in degrees Kelvin (K) and to convert C to K you must add 273 to whatever temperature is given in Celsius.  In this case we will start at a comfortable 25C and work our way down to below zero C.

On a 200bar system with a 500cc capacity tank, how is this affected by varying the temperature? Let's see!

If we fill our cylinder to 200Bat at 25C and then examine the pressure drop at the following ambient temperatures:

15C, 10C and 0C. 

In order to perform this calculation we need to first convert degrees celsius to degrees Kelvin by adding 273 to each degree C value.

Now we find that the pressures are as follows:

193 bar at 15C

190 bar at 10C

183 bar at 0C

For this PCP, the minimum recommended operating temperature is -5C, for which your starting pressure at this temperature would be approximately:

180 bar.

So we can see the gun is not  recommended to be operated below 180 bar.

Now these values are only what you see here as long as the volume of gas remains the same. So prior to shooting in cold whether check your actual gas pressure.

Hence for the safe operation and or optimal operation of a PCP air gun, the there will be certain limitations upon the functionality of the weapon due to whatever ambient temperature it is operated at and the duration of operation.

Operation outside of the manufacturer's specifications  range for temperature could prove fatal for the operator! Especially if one exceeds the maximum operating temperature (usually around 40C/104F).

However, it is unlikely that one will be shooting at 40C! it is more likely one could be shooting at temperatures lower than 20C/68F during cooler months of the year (if outside). 

BTW what would the pressure be at 40C?

Approx: 210 bar. Well within the safety limits of the original pressure vessel.

This is where I placed a small flexible and water resistant resistive heating element encapsulated within a Silyl ether polymer (can withstand temperatures up to 80C). The heater is powered from X2 AA alkaline cells and sits atop of the steel regulator cylinder of my Reximex throne. The closed cell foam is added for insulation.

Further testing is still required as the mass of metal associated with the regulator pressure vessel is very large and made from a lower conductive steel alloy.

I marked the "Power wheel' so to to be able to reproduce particular power settings on this PCP rifle.

We made a "custom camouflaged' AUTUMN lightweight bottle cover. (See video)

Using a Vortex Red Dot Crossfire sight for close range moving targets up to 25m.

The only other thing I did to this PCP was to replace a small diameter castellated metal washer (inside the grip-not shown) with several wider (but same internal diameter) stainless steel washers to help take up a very small but annoying "slop" in the grip and to evenly distribute the load from the grip bolt upon the plastic molded grip.

BCT

FITWELL BIG WALL TREK BOOTS

Well after absolutely astonishing service of almost 3 years, I have to say a partial goodbye to my FITWELL BIG WALL boots because the Vibram soles are almost bare and the uppers are starting to fail on me-EVER SO SLIGHTLY!!!

BUT!!!! this is only after wearing them EVERY DAY for almost 3 years! Hiking, camping, caving, fishing, hunting, in the snow and in the arid zones; MAN ALIVE this FITWELL BRAND rocks! No I'm not saying this because they gave me a pair of boots; no I BOUGHT THEM!

AND now I need a new pair So I decided to try something along the same lines but this time the FITWELL BIG WALL TREK.

Expertly crafted in Italy with Vibram soles just like my FITWELL  Big Wall BOOTs.

This is a super grippy but long lasting sole tread pattern from Vibram.

I know this EVENT membrane really goes the distance, in fact I reckon better than GORTEX!

The difference we see now is that there are eyelets on all the lower laces and metal lugs for the last two laces places.

The main difference is that the leather upper now reaches to the lower sole midway (instead of the rubber rand) because these boots are not intended for the super harsh side scraping big wall ascents but rather for light snow to 3 season usage. To be honest you would have seen me many times wearing my Big Wall Boots IN THE SNOW, albeit they were never intended for this activity because they are not designed for prolonged standing around in the sub zero weather.

Heavy rubber rands used where it counts for maximum friction and abrasion resistance. If you are not familiar with this type of boot construction, then let me tell you, this type of rubber is used in the construction of climbing shoes which encounter huge frictional forces and hav to last without failure against such forces. choosing to use similar construction methods for walking and hiking bots, mean that your boots will easily be able to encounter contact with rocks and other abrasive surfaces without any problems and in fact enable you to moe over tricky terrain.

Seriously thick synthetic reinforcing and accurate stitching tell the story of Italian made quality!

As the name says...............and believe me this is no idle boast by them!

FITWELL make this special inner sole that actually helps move the air around under the inner sole.

 Full event membrane lining, right up high on the tongue.

What more to say??? Do yourself a favour, the BIG WALL model has been personally blasted by me on every adventure excepting the full on snow, so there is is ZERO reason to think the BIG WALL TREK will not serve me the same.

The video Review

BCT

Pre-order your Extrema Ratio MF0 T ZERO now!

 

Pre-order your Extrema Ratio MF0 T ZERO now!

Get in quick for these guys!

Basically an "Instructor ZERO" limited edition run, 3 different anodized versions of the tanto version of the MF0, I think the olive green drab looks very funky!

Go to their web site for a pre order!

#MF0TZERO #EXTREMARATIO #EXTREMARATIOMF0TZERO

PCP Silencers from Nielsen

 PCP Silencers from Nielsen

Background

If you have only ever shot a rifle or pistol, you may be surprised to learn that the Pre-Charged Pneumatic (PCP) rifle discharge of only dry air, can be quite loud. Not loud enough to warrant wearing ear protection (IMHO). However, the sound levels will be somewhat dependent upon the following parameters but not limited to: the volume of expanding  air and the duration of that expanding air after the projectile has left the muzzle. of course this latter parameter should be minimised for optimal operation of the weapon and hence to reduce the unnecessary use of air from the tank. Generally for high quality PCP rifles, many parameters are able to be easily adjusted by the user.  Un-moderated sound levels can easily frighten game and of course disclose the position of the shooter , just as they can for a firearm.

One gun parameter that can not be adjusted by the user and that is the emission of sound, unless a moderator or more commonly known as a silencer, is used. The silencer for a PCP weapon works using a similar principle to that of a silencer for a real firearm. There will be a high volume expansion chamber directly adjacent to the muzzle, which will generally not cover the barrel unlike certain silencers designed for firearms. Following the expansion chamber there will be some sorts of baffles of proprietary designs to reduce the expanding gas velocity and hence limit the sound emission exiting the silencer. As for these baffle designs, well it appears there are a plethora of designs out there however, the only way to really judge whether they work or not is simply by measuring the sound emission in a standard way and conducting repeatable tests, regardless of whether these things are filled with "cosmonium alloys" from mines on IO or jelly beans!

In this blog and following video I will be exploring the reduction of sound level by using a high quality silencer manufactured in Denmark specifically for PCP weapons by Nielsen Gun Parts. I will be reviewing the following model silencer: SUB SONIC-35 0.22cal (Nielsen's range covers 0.177 cal to 0.22 cal) which forms part of the high quality SONIC line (21 different silencers across 6 different groups") of rifle accessories from Nielsen.

Nielsen Gun Parts is a Danish company and is part of J. Nielsen Design, who are staffed by experienced engineers with many years experience with hunting rifle and accessories manufacturing. Jørgen Nielsen is the man behind the designs, a hunter with over 40 years experience in weapons manufacturing. To find out more about Nielsen Gun parts see here

This is the SUB SONIC-35 0.22cal  (22-12158) silencer from Nielsen in Denmark (Danmark). 

It comprises of five "modules", the initial 1/2" x 20 UNF threaded female expansion chamber (or blast chamber in the case of a real firearm), followed by 5 conical baffles (modules). 

The construction of this model is entirely made from  aluminium and anodized black. 

Showing the 1/4" x 20 UNF female thread. (note a PCP adaptor of a male 1/4" x 20 UNF is required for mounting) to a PCP rifle.

Internal view of the first baffle/module facing the expansion/blast chamber.

The reverse side of the same module. Note all the modules on this silencer are the same. The shape here again allows for immediate expansion of gases.

For legal requirements, the silencers are not shipped assembled outside of Denmark (for obvious reasons), so what you see here is a fully assembled 0.22 cal SUB SONIC silencer.

All of the modules came with a generous (but not excessive) amount of grease on all threads to prevent binding. Since the test will be carried out on a PCP, unlike a regular firearm the use of high temperature resistant grease is not necessary in this case.

The above image shows the inside of the first chamber. 

The rifle for testing has an approximate barrel volume of 14ml.

The volume of discharged air depends on the rifle settings.

Nielsen SONIC silences come in a variety of thread sizes.

As the LASER engraving shows, Made in Denmark (and before anyone say's hey they got the spelling wrong-no they didn't! This is how Denmark is spelt in Danish.

You can see Nielsen's products here

 Stay tuned for the field testing Results on Bush camping Gear!

Extrema Ratio SATRE Neck Knife

Neck Knives

To be honest, I'm not a huge fan of neck knives. In fact over the years of running BCT and all the years prior to that, I have only owned 3 knives which one could call neck knives, that includes this one, the SATRE from Extrema Ratio. As apposed to "finger knives" of which I own 2 a Kizlyar Supreme Hammy and a Raidops LJ6GP. 

Pictured side by side, the Raidops LJ6GP in SV30 (6mm) and my new Extrema Ratio SATRE (5mm).

For me a neck knife is a kind of utility knife; firstly because the blades are so small and on the size of a tradesman's utility knife, ie around 1" to 2". One can use them for: all box opening procedures, cutting of small diameter cordage. Unless the blade is serrated (this one isn't) they are next to useless at fast cutting carpet and or similarly fibrous materials. 

The handle lengths are generally too small for a proper grip and or too uncomfortable; the blades lengths are no more than ones average Swiss Army Knife folder. They are in MHO and experience unsuitable for any sort of "survival" unless in highly skilled hands (even then such a small blade may be next to as good as not having one?). However, they do fall into the category of "if it's the only knife you happen to have with you", then you're going to be laughing. 

They are generally unsuitable for use in any sub zero environments essentially because one's hand can be frozen to  bare metal (many do not use scales to reduce weight).

I simply can not get comfortable with the idea of carrying a very sharp instrument around my neck.

The Pro's of a Neck type knife are the following:

Generally, the blades will be much more sturdy than any Swiss army knife and much more resistant to accidental breakage should undue forces be applied. So if you carry a SAK and only ever use the main blade, well a neck type knife might be even better, dependent upon the applications at hand.

 

I think for a neck knife to stand out in the crowd it must offer something different but what? Well one model of the SATRE from Extrema Ratio does just that, the SATRE, made from Böhler S600 Tungsten alloy tool steel (the regular SATRES are made with trusty old N690 from Böhler). S600 can be hardened to values used for milling and thus has a higher probability of staying sharper for longer cutting the same materials as a non tungsten alloy blade. There may be trade offs, such as possible increased brittleness but if cutting is all that is intended then this will not be an issue.

What about SLH???? That's Super Lightweight Hunting-LOL I just made up that term! Sounds good doesn't it? Well once a hunting buddy gutted and skinned an entire goat on a bow hunting trip with just a broadhead, whose one of two edges was a little shorter than the SATRE and no handle! So I reckon that could definitely be possible! Or taken as a backup hunting knife- not for butchering of course but gutting medium sized game and skinning, definitely! It is certainly easy to clean!

The main reason I don't carry a neck knife generally is that personally I always carry a locking folder either in my pack and/ or in my pocket and a much bigger (the size depends upon where I am going and for how long) fixed blade, the type depending upon whether I'm hunting, camping and or hiking and also depends upon the duration of the trip. The exceptions are for when I'm diving and then I always carry 2 dive knives without fail  a double edged and serrated dagger and a big partially serrated and monofilament cutter blade (more on this later).

Extrema Ratio SATRE in Böhler's N690

As to be expected the scabbard is well made and everything works out of the box. the profile is of course very slim and no rough things to dig into the chest if worn as a neck knife.

I've put some cord over my handle because for me, it's just more comfortable than the bare metal tang.

I took 2mm static cord (used by climbers and cavers for accessories) to partially cord wrap the bare tang. For me at least it makes it more comfortable and user friendly.

No nonsense easy clean

Here I easily cut up this chunk of meat and the whole knife can be easily made hygienic as there is nothing to retain dirt.

No trouble to dice an onion either.

The spine is a generous 5mm thick slab of N690 but it also comes in Böhler's S600 Tungsten alloy tool steel.

The Extrema Ratio Satre comes with a generous length of thick para type cord and quality looking cord lock. It will also be available later with a pocket clip made by "ULTI Clip" (Made in the USA). I have to say I use an ULTI Clip  on another EDC knife I own, and they work well for secure pocket carry. More on that later.

Stay tuned for a field review of the Extrema Ratio SATRE at BCT

 

Work Tuff Gear NOMAD EDC

in Japanese Hitachi ATS-34!

This is one high quality EDC knife from Work Tuff Gear. The Nomad EDC made with Hitachi ATS-34 martensitic stainless steel. A classic Japanese stainless capable of obtaining very high Rockwell C values, in this case 59-61.

The knife features a very very comfortable grip, that just feels perfect in your hand; made from contoured G10, with a full tang construction. I was lucky enough to get a hold of a first production mode because this steel is getting harder to source these days.just depends upon who bought stock many years ago.

The Nomad EDC features a sabre grind with a convexed edge. The blade is 0.145" thick ( is approx. 4mm thick).

The Orange colored scales (almost matches these delicious (kaki -Japanese for persimmons) are made from composite G10 and come with options of black, neon green (this model) or  blue contrasting liners.

The Nomad EDC comes with a well-made Kydex scabbard and a "ULTI" made in America pocket clip.

It also came with a WTG Fire striker ferro rod (more on this later).

As the name implies, the Nomad EDC is an everyday carry knife that can easily fit into one's pocket and does just that with the aid of the supplied "ULTI Clip" (made in the USA) clip which is perfect to securely hold the knife in one's pocket.

ATS-34 for those who are not familiar with this steel made by HITACHI of Japan.

ATS-34 was an original development from Hitachi steel in Japan many years ago.it featured 14% Cr and 4% Mo, with around a bit over 1%C and some Mn (0.4%) and Si (0.35%). It is no longer in production. ATS-34 if properly heat treated is a great performer. Many who say it was rubbish simply didn't know the exacting requirements for heat treatment. ATS-34 never was a stainless steel which was suitable for some "witchcraft-like" heat treatment. This alloy can easily obtain a hardness of over 59 and really hold an edge. For an EDC knife, as the name implies, will be carried and probably used daily, one doesn't want o be resharpening it every 20 minutes or even every day because if you spend like one hour on this chore, it's one hour out of your day (or night) full stop.

Easy to hold with or without gloves

This is an excellent knife for hunting, especially skinning game.

See my video field review here: