RWS 850 AirMagnum PCP Conversion - Part 2

By A.R. Tinkerer

Part 1

Last time we looked at the performance of a .22 caliber RWS 850 AirMagnum using air (actually nitrogen) instead of CO2. It was connect to the nitrogen source using a paintball remote setup. Today we will look at a different setup. This time the tank was filled with air, but that shouldn't make much difference.

Pressure
I was puzzled by the results from my first test so I began to figure out why the results weren't better. The first thing I did was to set up a pressure gauge on the paintball tank to check its output pressure. It read 800 PSI. Pressure for CO2 at room temperature is about 850 PSI, so that could explain at least part of it.

Next Step
At this point I decided that if the project was worth continuing, I might as well convert my 850 AirMagnum into a true PCP (Pre-Charged Pneumatic). I began to look for small tanks that would fit under the barrel and a paintball regulator that would put out higher pressure. I found a 13 ci (cubic inch) tank, a Smart Parts Max Flow Inline regulator, and put together the setup below. Finding the parts to connect everything was a challenge since I used only off the shelf parts. I did have to drill and tap one part.

RWS 850 AirMagnum PCP

The tank and regulator are connected to the adapter via paintball macro line. The Smart Parts Max Flow Inline regulator is great because it is adjustable and has an on/off built-in. Not only that, but it has a tank pressure gauge and an output pressure gauge!

Tank, regulator & adapter closeup

The adapter includes the Cooper-T AirSource to ASA adapter discussed last time plus a customized adapter with a burst disk, macro line connector and bleed plug. The customized part is a Palmer's Pursuit adapter that has been drilled and tapped for the burst disk and macro line fitting.

Adapter

The mount is made out of a Daisy scope mount. Rubber gasket material protects the barrel and a Lucky Paintball drop forward mounts to the regulator.

Mount

Testing the new setup
I planned to test the new setup by setting the regulator to around 800 PSI, shooting a couple of shots, then increasing the pressure by 50 PSI. I would continue until I reached 1000 PSI. That would give me a nice set of results for 800, 850, 900, 950 and 1000 PSI. With that spread I should be able to see what pressure the AirMagnum liked best. Things didn't go as planned. I set everything up, turned on the regulator, and the output pressure was lower than I wanted. I tried to adjust it and found that it wasn't easy to adjust the pressure with the air on! Ok, I figured I'll go to the maximum pressure and try to adjust down. Maybe that would be easier. I turned off the air, adjusted to maximum and was pleased to find the regulator put out about 1050 PSI. I shot a couple of shots and tried to adjust the pressure down. It was just as hard to adjust down as to adjust up! So I shot the rest of the tank at 1050 PSI and did some testing with the RWS compensator I had just purchased.

Results
This time I was shooting with a friend who owned a commercial chronograph. Unfortunately the light wasn't right or something else was wrong and we were only able to record the speed of one shot. That shot was 619 fps. At first I thought even that reading must be wrong, but after posting my comment on the Pyramyd Air blog, BB Pelletier commented that I might be experiencing valve lock at that pressure (1050 PSI).

Going futher
I didn't like the look of this new version and it was difficult to adjust, so instead of trying to test further, I decide to go back to the drawing board once more. At this point I am going to go backwards and explain the original design criteria. Then I will fast forward to the next design and the search for components to fit those criteria. Don't worry, I will post some intermediate results next time.

RWS 850 AirMagnum PCP Conversion - Part 1

by A.R. Tinkerer

Background
My start in airguns came in about 2005 with the purchase of a Crosman 781AK kit. I was unfamiliar with airguns and three of its features clinched the sale. The 781 is a single pump, multi-shot, BB and pellet gun. I don't remember why the dual ammo attracted me, but it did. I intended to use it for pest control and since I didn't shoot much, I wanted to be able to take a quick follow-up shot. I figured the multi-shot and single pump features fit this bill. This was also a spur of the moment purchase.

Fortunately, about that time, I came across the Pyramyd Air blog. After doing some reading, I began to realize the 781 was not powerful enough for pest control. So began my search for the perfect airgun. The RWS 850 AirMagnum had recently been introduced and seemed to be a good choice. If the Benjamin Discovery had been available at the time, I would have bought it (even though it wasn't a repeater)! This post also wouldn't be here (and probably not this blog). Anyway, I ordered the .22 caliber AirMagnum and couldn't wait to use it after sighting it in. Soon I had a chance.

To make a long story shot, I shot a pest that we had problems with. However, it wasn't a quick kill, so I decided I needed more power. I had read that using air in a CO2 airgun would increase the power, so I began to research a conversion for my gun. Later I discovered that one problem was that I should have taken a head shot.

The First Conversion

I did quite a bit of research on the web to figure out how to convert to air. What I found is that paintball is a great resource! My requirements for the conversion were to keep it simple and use off the shelf parts, and most of these were available from paintball stores. But I had one problem. I couldn't find an adapter to convert the AirMagnum's Crosman AirSource connection to a paintball ASA.

Some Paintball Terms

ASA - Air Source Adapter, the adapter a paintball tank screws into

HPA - High Pressure Air; high pressure air is sometimes used instead of CO2 (carbon dioxide)

Marker - official term for a paintball "gun"

Remote - setup that connects the paintball tank to a paintball marker

One problem I had with finding an adapter was that I didn't know exactly what I was looking for. I started thinking about how I could cut off the threaded part of the AirSource bottle, drill it, thread it and other creative ideas. It all seemed like a lot of work to me!

Crosman AirSource cut open

Finally I ran across an AirSource to Paintball adapter from Cooper-T. That was the ticket! It was a Crosman AirSource to ASA adapter with a check valve. After buying the adapter, I also bought a relatively inexpensive HPA tank and remote. I had everything I needed!

Remote quick disconnect; Cooper-T adapter (red)

Remote with Cooper-T adapter

A note about Cooper-T
Unfortunately the man who ran Cooper-T passed away. The Cooper-T web site is still up, apparently to clear out inventory. There are some complaints on the web about long waits getting Cooper-T parts now, but that may be understandable given the circumstances. Other sources for AirSource to ASA adapters have become available recently. My condolences to Cooper-T's family.

Results
Now that I had my conversion, I was anxious to try it. I found instructions for a DIY chronograph and set up my own. For my setup, my first paper was 5 feet from the gun and the second paper was 10 feet from the first paper (15 feet from the gun). I set the microphone recording volume to 50% (but NO microphone +20dB boost) and started recording.

The conversion of the .22 caliber 850 AirMagnum performed as follows with Nitrogen. I used Nitrogen for this test because the paintball store I filled at only filled with Nitrogen. JSB Exact Jumbos were used for the test and velocities ranged from 591fps up to 602fps with an average of 594fps (12.38 average foot pounds). That makes this setup about the same as CO2 on an 80 - 90 degree day. (The CO2 results for comparison came from comments on the Pyramyd Air blog.) It was 73 degrees Fahrenheit the day I tested.

Disappointing Results?
Was I disappointed with the results? Yes. I was hoping for better than CO2 performance, not just the same as CO2 at higher temperatures. The tank and remote setup is also kind of clumsy.

Things Learned
-Know what power level you need for hunting different size pests.
-Know where to aim to be humane when hunting. This may be different than where you would aim with a firearm.
-Quite a bit about paintball, high pressure air and air fittings.

What Now?
I have gone through a couple more versions of the conversion that I will describe in future posts. When I am done with my latest version, I will also post that. Following are a few projects/discussions I am planning for the future.
-Discussion on air power feasibility: problems and some solutions
-Discussion on possible uses of air power
-More installments on the RWS 850 AirMagnum conversion
-Air powered R/C plane
-DIY chronograph (using phototransistors)

Introducing AirNergy

by A.R. Tinkerer

Welcome to the AirNergy blog (note that the blog name has changed to PneumoNergy since AirNergy is a registered trademark of Global Energy; WindPower, Inc.)! This blog is to document building or modifying devices that use air as their energy source. For each project, I will try to include the original idea, the design, construction, tools used, problems encountered and things learned. Projects may get sidetracked to describe making or modifying something needed to complete a project.

This blog will not be updated daily. I don't know how often I will post, and it will vary.

Background
Following is a list of some of the experience I draw from so you have an idea of my background. You will see where some of these come in later on.
electronics hobbiest
high school general shop (printing, drafting, woodshop)
high school metalshop (mostly stick welding and metal lathe)
high school chemistry
high school physics
college physics

I am only an amateur and make mistakes. I hope I learn from them and by seeing my mistakes, you can avoid similar mistakes. I also look forward to learning from you.

Where Credit is Due
I must stop here and credit two sources which peaked my interest in what compressed air could do. Those sources would be the MDI air car and airguns. But that isn't the end of the story. Tom Gaylord, AKA B.B. Pelletier (Pyramyd Air blog), was the one source that is probably most responsible for feeding my interest. Thank you Tom!

I also must give HUGE credit to all of you who post information about your projects! These have been a great resource for me. I will try to post links to any web references I use in my projects, and list books, magazines, etc. that I use for reference.

Finally, I must thank God who gave all of us the ability to think, reason and create.

Lets get started
To kick things off, here are a few links I found interesting that relate to using compressed air for an energy source. There is one other link I wanted to include under the "Hands On" section, but I couldn't find it. I will post it when I do.

Compressed Air Engines
http://www.engineair.com.au/
http://quasiturbine.promci.qc.ca/
http://www.fuellessusa.com/AIR.html

Hands On
http://www.obilaser.com/AirPoweredTeslaTurbine.html
http://www.instructables.com/id/Air-powered-bicycle./
http://www.mocpages.com/moc.php/8844
http://home.ctlnet.com/~robotguy67/classic_cars/air_engines/V-Twin/air_engines.htm

Air Car
http://www.mdi.lu/eng/affiche_eng.php?page=accueil
http://www.theaircar.com/

Jay Leno's Green Garage (note the link to the wind turbine)
http://www.popularmechanics.com/greengarage

Next
The next post will introduce a project to convert an RWS 850 AirMagnum CO2 (Carbon Dioxide) airgun to use HPA (High Pressure Air). I will explain why I started the project and its humble beginnings.

And finally I must make a disclaimer.

DISCLAIMER: This is not a how-to blog. It is informational only (to explain how things work). Working with power machinery is dangerous and some of the things I will build are dangerous. WHATEVER YOU DO IS AT YOUR OWN RISK.