by B.B. Pelletier
This post is a direct response to a comment that came in last week:
A gas ram airgun is a spring gun…without a spring!
A gas ram airgun is a spring-piston gun in which the coiled steel mainspring is replaced with a sealed “gas spring” unit. Instead of the coiled spring pushing the piston, compressed gas does the job. “Gas ram” is just one name for this powerplant. It’s also called a gas strut and a gas spring, which I prefer because it is more descriptive of the unit.
You find gas springs in many mechanical things these days. Cars are probably the most familiar. Anyone who owns a minivan has seen a gas spring unit push the deck up when it’s opened. Gas spring units have all but replaced coiled steel springs.
Gas spring advantages
There are several advantages to gas springs over steel. Here are a few:
1. They last longer. Gas springs last for decades, while steel springs wear out in the same timeframe. Gas springs seldom leak, so it doesn’t matter whether they are under tension or not – they still retain all their power. Steel springs fatigue over time if they’re under tension. You can leave a gas spring gun cocked for weeks, and it will not lose any power.
2. They are lighter. A gas spring unit, which includes the piston, will shave off close to a pound of the rifle’s weight.
3. They are faster. Gas springs react faster than coiled steel, so they get the pellet out the muzzle quicker. They tend to be more powerful than equivalent guns with steel springs, but that can easily be adjusted with piston diameter and stroke length.
Gas spring disadvantages
Very few disadvantages, but you should know what they are before you buy a gas spring airgun:
1. They are harder to cock. For muzzle energy equal to a conventional coiled steel spring, a gas spring can tack on another 50 percent to the cocking effort.
2. They have a harsher firing behavior. They don’t vibrate like steel springs, but the jolt when they fire is quick, sharp and objectionable to some shooters. They also tend to be harder on some scopes.
Ten years ago, there were real choices in gas spring airguns. Theoben, the British company that made them popular, was selling a large line through Beeman, plus some people were importing the guns straight from England. The Weihrauch company put a Theoben gas spring into the Beeman RX, which is the RX-2 today.
RWS imported the RA800, which was a wonderful mid-level breakbarrel. Then, Vortex started selling gas spring units so shooters could convert their Weihrauch and Webley guns from steel springs. They were available for the R1, HW77, Beeman Kodiak, TX 200 and a few others. Today, only the Beeman RX-2 is still available in the U.S.
Is a gas spring a good powerplant? Absolutely! Is it the best? That’s hard to say. Read the advantages and disadvantages and decide for yourself.