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.
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.
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.
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!
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.
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.
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).
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.