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Bite The Bullet

Snipers: Gas or Spring? (2009-05-29)

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Sniper rifles. Many airsoft guns lay claim to this title on the box, and they come in two main flavors; spring and gas. For a long time there have been debates and discussions online about the merits of each platform and which is the better sniper. The two sides each have their good points and bad points and in this article we will discuss them.

Spring snipers are the cheaper option and thus you see more of them on the field. several companies make spring snipers including Tokyo Marui's VSR10, Maruzen's APS series, and the Sun Project M40. There are many more but the basic concept of them is simple. You pull a bolt which locks a spring inside it in a compressed and tight position, then pull the trigger to release the tension in the spring and propel forward a piston forcing air behind a BB and through the barrel. This is the most simple sniping solution, and it works. It provides an accurate stable sniping platform that can provide consistent groupings and always hit a man sized target at good range.

There are three main disadvantages going against spring sniper rifles. First and most noticeable is the stiff bolt pull. Due to the nature of the design, the energy for the shot comes from you manually bulling back the spring between every shot. For lower powered snipers this is not much of a problem as the spring is weak but for serious, upgraded, sniping, this can become a problem as it tires your arm quite quickly if you need to make many successive shots. The stronger the spring, the stronger the shock as it hits the front of the cylinder. This sends reverberations throughout the gun and vibrates the barrel. this vibration is detrimental to the gun's accuracy and can cause the occasional shot to stray wildly off target. This phenomenon present on all guns, and this is what prevents the groupings from being as tight as they could be. The third and final disadvantage is the long cylinder. The long cylinder means that the magazine must be located in front of it, being both unrealistic and shortening the potential barrel length. Despite these disadvantages, the spring sniping platform is still the one of the most popular sniping platforms out there.

Gas powered sniper rifles are more commonly seen among the more weathered snipers in the field. This could be due to their higher cost and complexity of use. Gas sniper rifles have found soft spots in sniper's hearts and minds (no pun intended) due to a more realistic action and a lighter bolt pull. They also make a nicer sound when fired. Gas powered snipers are often push-cocking. which means the firing pin is cocked as the bolt is pushed forward. The push cocking mechanism and lack of long spring means that the magazine can be located further back on the gun, in the same location of the real gun. This results in a longer barrel length as the barrel can start from a further back position.

This variety of rifles comes with it's own array of disadvantages. Even though there is little vibration in the gun as it shoots, the gas expansion that is required to propel the BB causes the liquid gas in the gas reservoir to cool down. This in turn causes the pressure to drop and thus the power of the subsequent shot to be lower than the previous if the magazine (or other gas storage solution) is not allowed to return to the original temperature. This temperature dependancy extends to the entire rifle performance itself. In winter conditions and high humidity all gas guns do not perform as well as they can. to demonstrate this fluctuation of power, we fired 15 shots through a chronograph from a gas sniper and a spring sniper. the gas sniper varied between 361 and 418 FPS (57 FPS fluctuation) and the spring sniper remained between a more constant 284 and 296 FPS (12 FPS fluctuation).

To help settle the debate over which makes a better sniper we have chosen two sniper rifles representative of their class and had a face off. Representing gas rifles is the Tanaka L96 covered rifle, at 430 FPS and a barrel length of 640mm. Representing spring rifles is the popular VSR10 from Tokyo Marui, at 300 FPS and a barrel length of 320mm. Both guns were zeroed and both guns were put through about 100 rounds before the test to ?break in? the hop up as is necessary for some airsoft guns fresh out of the box.

A simple accuracy test down a 15meter windless corridor was conducted. And each rifle zeroed and fired through ten shots at a 20cm target. Here are the results:

 

The vertical spread of the VSR 10 was only 62mm and the horizontal spread was 59mm. The furthest distance between hits was 78mm. The similarity of the vertical and horizontal deviation attests to a consistent hop-up and the groupings were above average for any stock airsoft gun fresh out of the box.

The vertical spread of the L96 covered rifle was a slightly larger 70mm and the horizontal spread was 78mm. The furthest distance between hits was 94mm. This shows the L96 being the slightly less accurate gun of the two, but not by much.

To draw a conclusion from this test would be hasty as only two guns were tested and only once.

Now we shall look at the reasons behind this difference. The primary difference in the two guns other than one being gas and the other being spring is the length of barrel and type of hop-up. Although the L96's barrel is longer, it has no spacers on it, thus the barrel is left to resonate freely from the impact of the hammer and the shock of the BB traveling through it. This lowers it's accuracy but not by too much as it is a gas weapon and there is less shock from a heavy spring to vibrate the barrel. On the other hand, the VSR's much shorter barrel has a spacer placed in an irregular position, perfect for dampening the vibrations of the strong spring. The major difference in the hop ups is that the Tokyo Marui VSR comes with a V-Hop. That is a hop-up which has a bucking that applies pressure on two points of the BB instead of one, creating a more consistent backspin. The Tanaka L96 doesn't have this. Instead, it has a standard hop-up which applies pressure evenly across the top of the BB to create backspin.

The proper method to apply spacers is to place it into an irregular position to minimize resonance
Placing the spacer in the center still allows the barrel to resonate, decreasing accuracy.

 

The L96 has no spacers to prevent resonance in the barrel.

 

Despite the Tanaka L96 having a slight disadvantage in accuracy, it is still a very accurate gun and much more powerful than the Tokyo Marui VSR. This gives the L96 more range than the VSR straight out of the box. However, the VSR's better hop-up and simpler system gives it more accuracy and reliability. Look for more articles on sniping in the coming future.