1600 f.p.s. pellet rifle
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  1. #1
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    Someone was mentioning "Getting a 1600 FPS pellet rifle barrel.I found the Gamo Hunter Extreme rifle that reaches this velocity.It shoots PBA Raptor non lead,14 k. gold plated pellets.What I want to find out is,is this velocity the result of the pellets being very lightweight?The pellets claim 25% velocity increase.Is it the rifle?Someone mentioned "buying the 1600 fps barrel".I couldn't find the barrel for sale.Does anyone have experience with this rifle,the pellets,or has purchased the barrel?I don't see myself how just the barrel alone could deliver that velocity.I'm wondering if the pellets are light,and slow down rapidly.Anyone know about this topic?

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    Heya GW,

    The advent of maximum velocity pellet guns has been somewhat of a game over the last 40 years.Some time ago Weirach produced a rifle called the "Barracuda" that used small dose injection of "Ether" (The medial compound not all the free energy stuff) and also designed a 22 Grain slug that still holds that name to this day (The H+N Barracuda).
    The uypper sensible limit of pellet guns is approx 1035 fps at ambient pressure as after that vorticular motion and drag become a huge issue.(They may go fast but do they go straight?)
    Simple physics are usually the cause of the "Extreme velocity" guns that are on the market.
    Take for example a typical .177 pellet weighing 7 grains.

    MV of 850 fps / squared *
    Projectile weight in grains / 450240

    11.23 FtlB roughly...thats under the UK's harsh limit for a pellet gun without a licence.
    1600 fps with the same slug
    39.8 ftlb (ties in with the old "double the velocity and get 4x the energy)

    The barrel will have NOTHING to do with the velocity,the barrel does not provide the energy and it's the energy that gives the pellet the ability to do "Work".
    Length of barrels can make a small difference to a pellet gun but by far the biggest contributors are

    In a spring gun:

    Swept volume of the cylinder.
    Diameter of the air transfer port.
    Open pressure values of the spring.

    In a precharge (Air not c02)

    Volume of air discharged.
    Pressure of air discharged.
    Length of barrel to allow expansion and acceleration.(remember the laws of diminishing returns though,over a certain length and drag becomes a problem)

    As to the claim that the pellets alone deliver a 25% velocity increase this will certainly be a matter of weight.

    Input power * efficiency = output energy (simplified)
    Anybody that tries to sell you a pellet gun barrel claiming it will give more than a 10% increase in power/velocity with the same projectile is a fraud.Most spring guns operate at around 15% efficiency,most precharges operate up to around 75% efficiency.
    There are some other things that can affect the energy/velocity/projectile weight issues but all of those are still based in standard physics.

    The Raptor pellet btw is gold plated pot metal or Zinc alloy.Higher velocity is aproduct of it's weight.

    cheers Dave

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    Thanks,dave.I was pretty sure that the high velocity had to do with the pellets probably being lighter.I didn't see how the barrel could make much difference.Since someone mentioned "getting a 1600 fps barrel",I wanted an extra opinion on it.Now,if you could figure out how fast a tightly rolled wad of paper could exit the barrel,we could probably work up some REALLY high velocity!!!!My most accurate spring air rifle is a Walther,can't recall the model.Abt.600 f.p.s..My 1000f.p.s. rifle will only group the size of a dime at 30'.The Walther will group ONE bullet hole at that range for 5 shots,IF I can hold it to do so once in a while.By the way,I have both a .177,and a .22 BSA air rifles ,pat.date 1907.Also have a Webley,abt.1927? that has a considerably smaller air chamber,but superior automotive type piston rings.The Webley will hit just as hard as the bsa's.It's really surprising.Just seals better.

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    Hiya Gw [img]smile.gif[/img]

    Bit more random info having done some research today.
    The Gamo PBA pellet weighs 5.4 grains and is of the nominal "shuttlecock" shape.
    I noted with interest some of the retailers swelling the abilities and properties of these pellets.A few basic airgun facts they left out though are as follows [img]smile.gif[/img]

    ALL spring piston air weapons use the fundamental priciple of controlled "deiseling" ie:they deliberatly burn a tiny fraction of the cylinder lubricant in order to provide a considerable amount of the total energy.(See earlier note about miserable efficiency of spring powered guns).
    To test this out,degrease your springer of choice and then reassemble,watch the muzzle energy drop by as much as 60%! By adding low flash point liquids at (for UK legal reasons) unspecified quantities any springer will easily exceed the sound barrier.(At much less cost than a Gamo Extreme).

    The posted muzzle velocity of the Extreme is 1600 Fps,this will be in lab conditions with a new blueprinted gun no doubt but lets accept these figures at face value.Plug in the maths

    1600 * 1600 * 5.4Grains / 450240 = 30.07 Ftlb of energy at the muzzle.
    Now 30FtLb may sound a lot but when compared to say the humble .22 rf it suddenly doesn't seem so much.No matter that's still impressive energy for a pellet gun(Airgun)?
    Or is it?
    I have in my collection a Robert Jones .44 cal aircane manufactured some 120 years ago that after some effort in pumping up to the required 900Psi gives around an average of 560 fps with a 200 grain round lead ball.Back to the maths.

    560 * 560 * 200 / 450240

    139.30 FtLb.....say whattttttt 139 Foot Pounds!

    Umm so that means in theory if the energy is available then reducing the projectile weight is going to give me more velocity? same maths in reverse but using the 5.4 Grain PBA pellet.

    Energy * 450240 / 5.4 then get the square root of the answer giving us a very *rough* figure of 4400 fps...somewhat making the .50bmg slap round look slow.Now in the real world this isn't going to happen(due to a number of physics restrictions as yet nobody can work around)but it does illustrate that quoting muzzle velocity figures to sell guns with providing the rest of the additional information is a little like selling a 200 mph car with no brakes.

    Final item of interest is the age old Weirach HW80 std springer.The model imported into the UK is set to work at a given energy of circa 11.5 FtlB (due to our laws) however it may come as a supprise that with $10 worth of modifications it can easily produce up to 60FtLb of muzzle energy.This can be with any resonable pellet weight and any of the std calibres.(the most efficiet being the .22) but it can easily outclass the Gamo in both perfomance,accuracy and build quality (the Rekord trigger unit has yet to be surpassed by pretty much ANY std gun available in the world).For legal reasons I cannot post publicly what those mods are but if you care to drop me a line I'm happy to give you the details (you being somewhere with less restrictive laws).

    Finally without boring you daft with the details here I can also state that the shuttlecock (or waisted) design of the PBA projectile is renowned for being one of the worst possible balistically speaking in any weapon that exceeed the circa 1100 fps sound barrier.In slow motion in a vortex analyser the eddy/wake and vorticular motion of the air around it is quite a piece of art.It's actually supprising that it's possible to hit the proverbial barn door from inside the barn with it.Throw in the fact that pointed pellets rarely if ever have the point to the Nth degree of concentricity you will likely find that only professional writers who have advertising revenue to consider will find them to be anything more than the gimik that they really are.

    On the subject of guns though


    A project I designed and made about 2 years ago.
    11mm calibre.
    Airpowered.
    sub moa at 100 yards.
    300+ FtLb.

    sorry to ramble as usual

    best wishes

    Dave

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    Great piece of work,dave,but,is it legal?

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    Hiya GW,

    Yes it's legal,it was made with all the required paperwork for use as a security "control" weapon for use in an oil refining environment in Saudi where stuff like muzzle flashes etc could do a few million $$$'s worth of damage.Even the ammo it fires is non lead and non metallic to prevent sparks on impact with any of the super structure [img]smile.gif[/img]
    The entire weapon is aluminium alloy including the gas ram that replaces the tube actuation spring.Everything is anodised to prevent static build-up as well [img]smile.gif[/img]
    These days I spend my time building weird custom airguns and moderators of all kinds.(not as much fun but it pays well)

    best wishes

    Dave

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    It's a beauty, per chance plans available?

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    Thank you for showing that great piece of work,Dave.What is the muzzle velocity of your airgun?

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    Am,

    I don't own the design anymore,that was part of the contract when I designed and built it.The current owner may or may not release the design drawings,I have no idea.I can however let you have the pictures taken in the manufacturing stages? it's resonably easy to work out from there.

    GW,
    Just under 1950 fps using the high density non metal ammo.The projectiles looked like Flechettes and were quite long but only having limited power available I had to compromise somewhere.
    The most powerful air powered gun I ever worked on/designed fired slug rounds for a total of 780 ftlb of energy but had a very low velocity (they were training rounds for shotguns) the most unusual is an air powered shell that was used for no emission discharge of both baton rounds and 40mm grenades.The grenade version never took off but the baton rounds are in use by the UK police at their training ground in Hounslow in London to save on costs as they are refilled from a large capacity divers tank and have a useful life of around 600 shots before the seals need replacing.(seals cost about a buck a set so it was well cheap)
    My toy cupboard is full of projects that some of which worked and sold well and some turned out to be white elephants [img]smile.gif[/img]
    I used to post a lot of the drawings on the web for people to use as they saw fit,then issues of liability and morons not reading instructions got to be too much of a risk so I stopped doing it.
    These days it's mostly moderators that take up my time,they have great markup value and new designs are reasonably easy to come up with.

    best wishes

    Dave

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    DAve, I would like to know the valve and hammer arrangement. The format is kinda Airforce like.
    Please post some of those pics if possible. What a beaut.
    Walter..

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    very similar Walter [img]smile.gif[/img] just with a Bias valve to allow more air out.The valve was open both ends so there was similar pressure trying to push the valve stem out of the back as there was pushing forward holding it closed.It meant that I could use a much weaker hammer "spring" and still dump huge volumes of air through the barrel.
    I was using much higher than normal pressures as well...circa 450 bar instead of the more usual 240 to 300.
    I'll get some pics zipped up and post them [img]smile.gif[/img]

    best wishes

    Dave

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    Here ya go Walter,I've taken out the image tag so they shouldnt slow down the page load too much..(I hope)

    I'll get some better pics up at the weekend.It went through a number of guises from an 11mm slug to 11mm diabolo shape to the final version that fired flechettes.

    http://www.exsecratio.com/raven/2.jpg

    http://www.exsecratio.com/raven/3.jpg

    http://www.exsecratio.com/raven/4.jpg

    http://www.exsecratio.com/raven/5.jpg

    http://www.exsecratio.com/raven/6.jpg

    http://www.exsecratio.com/raven/7.jpg

    http://www.exsecratio.com/raven/8.jpg

    http://www.exsecratio.com/raven/9.jpg

    http://www.exsecratio.com/raven/10.jpg

    This was the completed 11mm diabolo gun before I changed the entire thing to flechettes...(well it seemed like a good idea at the time)

    http://www.exsecratio.com/raven/overview.jpg

    I added and removed different magazine formats as well,but ended up using a simple single shot design as the customer was worried about gung-ho users shooting up oil tanks with a mag fed weapon .

    best wishes

    Dave

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    Dave, thank you very much!!!!!
    I am most interested in this airgun. I made my own scratch built Condor with many barrels. With the 9mm I achieved 175fpe at 3000psi (the MAWP of my bottle) I see you are using a tube reservoir. I am most interested in your balanced valve as the valve and hammer arrangement is a limiting factor on this coaxial design. I await more info with baited high anticipation [img]smile.gif[/img] [img]smile.gif[/img] [img]smile.gif[/img]
    Walter...

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    Hiya walter,
    I'm a little limited to what I can post about the valve design as the design and rifle were purchased on a contract by Tactical Electronics & Weapons Systems Ltd in the UK.
    I can give you a few tips to *look* at and *consider* though.

    The biggest problem in getting energy is either the pressure it takes to overcome the valve diameter or the weight of the hammer spring.
    This is a result of the area of the valve exposed to the atmosphere at the front of the bottle.
    If that pressure is all going forwards then the valve can take quite a pressure to knock open.
    Imagine you can divert some of that pressure by having it act on the same kind of valve that tries to open to the rear?
    Imagine a picture of a valve running right through the bottle with maybe a spring that sets the bias towards the front end? 6000psi trying to hold it closed at the front,VS 6000 psi trying to pull the valve stem inside the gas tank at the rear...4 to 6lb closed pressure spring ensuring the valve goes forwards and not backwards...
    Valve action under pressure....oposite and equal....
    Spring pressure giving bias...
    To fire ..overcome spring pressure..

    Let's imagine you building a fizzy drinks maker,that 900 +/- psi of gas pressure is going to take some overcomming to get the C02 into your fizzy pop isn't it...
    If you were to prepare you fizzy pop maker using only Gaseous Gas as it were you would probably go for a bias valve similar to this sort of thing?



    In most cases it may pay to look at using the gasses own pressure to do some of the work in your fizzy pop builder.Few extra holes to vent pressure...maybe a double check to make sure your not side loading an o-ring over a hole..
    It's supprising what day to day items can be adapted for other purposes isn't it?

    best wishes

    Dave

    ps:valve balance,working diameters,or should that be loaded diameters is always critical of course [img]smile.gif[/img]

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    Dave,

    Many thanks for the photos posted. After reading additional post I do understand about the contract work for any defense industry, any additional photos and info you can provide will be appreciated.

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    One trick that might get a 1600 fps barrel would be to taper the barrel from .22 cal. to 20 cal.

    The moa would probaly s**k.

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    Aug,

    Wasn't that done some time ago...German gun as far as memory serves....

    Vom Hoff Express rings a bell?

    Air powered guns vary in Efficiency,the bigger the bore in genral the more efficient the air is used.Doubling the bore size can work out at 4 times efficiency (subject to deminishing returns etc)That's the reason airpowered spud guns can reach 100+ ftlb with a low operating pressure (under 100 psi)
    .177 air rifles have springs around 40% higher powered than .22 rifles of the same make and model.Squeeze bores do provide more pressure but it's spread over a smaller surface area and against a larger drag coefficient (pellet to barrel wall compression)
    The old story of putting a .22 spring into a .177 gun actually has a reverese effect on power(by quite a lot)

    Am,

    I'll see if I can dig out some of my other designs I never proceeded with,your welcome to use them as you see fit [img]smile.gif[/img]

    best wishes

    Dave

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    Dave, thank you. The drawing shows clearly how you achieve the larger porting. I am curious how you load your gun as the breech seems smallish in the pics. Wonder how many 300fpe shots the tank will give you?
    Very nice and PLEASE post more of your airgun ideas. Very happy to digest them.
    Walter....
    BTW a tapered barrel as in 0.020" of taper would likely end up a plugged piece of scrap steel
    IMNSHO

  19. #19
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    I worked on a ballistic compressor design in the late 1970's, basically a 4" bore air gun with a cap over the end of the barrel where the 150,000psi needed for experiments was produced by 1500 PSI in storage tank.

    The valve was pilot operated, that is pressure balance kept it closed until one side was vented.

    Care was needed to make sure valve reseated when setting up for another shot.

    Seems to me three problems in air gun, one getting the propellant gas out of reservoir fast enough to keep increasing volume pressurized behind retreating pellet (valve max flow rate), second getting the valve open all the way fast enough, so pellet doesn't get out of barrel before it sees full driving pressure; three is speed of sound in barrel behind retreating pellet. With burning powder, high temp increases speed of sound, but how can a "cold" air charge expand (and keep pushing pellet)faster than sound?

    Nor sure I believe the Diesel idea, I think poor performance of dry gun due to higher friction between piston and wall, and loss of sealing by oil film.

    Straighten me out, please!

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    Dave, what about putting .177 spring in a .22 air rifle?
    Nial


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