Living in New England, outdoor CO2 airgun shooting is definitely a three season affair. However, as the WLOPA club shoots silhouettes year-round, and I have an affinity toward my TAU-7 Silhouette and Aeron Chameleon, which are both CO2 powered guns, the quest began to find a good was to keep a CO2 supply and gun warm enough to shoot outside during winter months.
My thinking was that if I could keep the gun and it’s CO2 bottle reasonably warm, I could pull it out of its case during a stage of fire, complete firing, and immediately return the gun to its carrying case for rewarming. The thinking was that the periods of rewarming would allow the gun and CO2 to stay at a reasonable average temperature that would allow enough pressure for winter shooting.
As the quest to build such a system began, my first idea was electric sox. After all, they do a great job of keeping feet warm for extended periods of time during the winter. So, off an order went to Cabela’s for a pair of electric sox to put my gun and CO2 bottle in between stages of fire.
Only two words can describe this first experiment – TOTAL FAILURE! As it turns out, electric socks are designed to have only a small heating element in the toe of the socks that was totally inadequate for the job. In this experiment, on a 50 degree day, I only managed to keep the gun at about 51 degrees, and measuring that temperature accurately was a challenge. But we’ll get to that in a moment.
After an evening of thinking and browsing on the internet, I decided that what was needed was an electric blanket to wrap the gun and CO2 in as well as a case to store everything in. The case was the easiest part – a lined shotgun case available at most sporting goods stores.
For the electric blanket, something portable was needed.
This meant that the blanket would need to be plugged into some sort of
electrical energy source like a car battery. However, using a car battery was
out of the question due to size and weight restrictions imposed by the case in
which all elements needed to be maintained. The electrical blanket that was
ultimately chosen for the task was a nifty pet-sized electrical blanket that
could heat up to 125 degrees F. This was found at
http://skingcompany.com/detail.asp?product_ID=PB24
The next piece of the puzzle that needed to be solved was an electrical source. As stated, a car-sized battery was out of the question. I reasoned that one of those units that can be plugged into a cigarette lighter for emergency use in starting a car during a cold day would work. With a quick trip to Radio Shack, I obtained an emergency, rechargeable battery for the power source. The initial results with this rig were promising as I was able to warm a gun and CO2 tank to 80 degrees on a 50 degree day. However, the battery was not a deep cycle battery and only supplied enough power to warm the gun for about 30 minutes – not nearly long enough for a shooting match that could go for several hours and in much colder weather than that which the tests were conducted.
Armed with the knowledge of need for a bigger battery, it was back to the internet to learn about portable power sources. This led me to the MK Battery company (http://www.mkbattery.com/). MK manufacturers and entire line of lead acid and gel cell batteries in a variety of sizes and configurations. The battery I chose for my application was a slim-line gel-cell battery that delivered 7.2 amps for a period of 20 hours when fully charged. Having the battery in gel-cell configuration was an added benefit as this eliminates the possibility of acid position due to leakage.
With a little bit of wire cutting and battery terminal clamp installation, I had the heating blanket hooked up to the battery and really throwing off the heat! At 50 degrees F, I was able to raise the temperature of both gun and CO2 cylinder up to 117 deg F in a little over 20 minutes. Whoa!!!! However, this presented a problem because the heating blanket has a circuit breaker that tripped at 125 degrees. So, now that my heat source, and heating mechanism issues were resolved, I needed a convenient way to monitor temperature when the gun was wrapped in the heating blanket and inside the carrying case.
This led me back to the internet to do a search on portable digital thermometers. The search led to a company called American marine (http://www.americanmarineusa.com/). American Marine manufacturers a line of tropical fish tank thermometers that contain a low powered radio that continually signals temperature at a probe on the end of a long wire (for submerging in a fish tank) back to a handheld digital readout device that can be maintained up to 50 feet from the radio transmitter source. To make use of this device, I simply placed the temperature probe in the middle of the electrical blanket and put the monitoring device into my pocket. Perfect!
This setup accurately measured temperature within the blanket and of the gun and CO2 cylinder contained in the blanket. So that I could quickly turn the blanket on and off to avoid overheating, I added a toggle switch into the blanket electrical cord and mounted it on the carrying case. Now should the temperature exceed 90 degrees, I simply turn the circuit off by hitting the toggle button or opening the case to let some cool air in.
I thought about the possibility of adding a thermostat to keep the temperature within a narrow range, but ultimately opted against the thermostat because on a very cold day, I want maximum heat to warm the gun up as quickly as possible after a stage of fire. As a final touch, I installed an emergency warming blanket between the outer shell of the electric blanket and the actual blanket heating element to reflect as much heat as possible back into the containment area for the gun and cylinder.
During the past year, I have had an opportunity to test the function of the heating rig on several occasions, and learned that it is possible to keep a gun and CO2 cylinder between 68 – 80 degrees on a day as cold as 27 degrees F. That’s OK, because if the weather gets much colder than that, I’m not going to be out shooting anyhow!