The Basics of High Pressure vs. Low Pressure

As many of you know, pressurized air is a large part of a marker’s operation. Most of you also know that pressure varies from marker to marker, and that the companies who engineer and produce these markers often use pressure as a method of marketing…but do their claims about pressure really hold truth?

In the old days, as some of you remember, low pressures were advertised to give the paintball a flatter trajectory and more distance, as well as lessen the noise report of your marker. Physics has since proved the first wrong, being that one non-rotating sphere moving at 300fps will go just as far as another non-rotating sphere moving at 300fps. However one cannot deny it was a very effective marketing strategy “back in the day”.

As time passed, many of these marketing methods were proved incorrect and slowly they were seen less and less until it was nothing more than “low pressure operation”…but what is low pressure operation and what makes it better than a higher pressure?

Before we put them head to head, let’s analyze what each one is. A high pressure marker generally operates between 750psi and 850psi, about the pressure that co2 is at room temperature. Because many lower end markers are designed to operate primarily on co2, they generally run around 800psi and are thus considered high pressure markers. Many older marker designs such as the AGD Automag and nelson valve pumps are best suited for a high pressure input. Low pressure is a little different. Many markers currently in production operate far below 800psi, some as low as 85psi. Most low pressure markers are in the mid to upper price range, which makes many believe that a lower pressure is in fact better.

The difference between low pressure and high pressure should be self explanatory, one is high and one is low. As simple as that may sound, the byproducts of each can get very complicated and confusing, so bear with me.

Because air at a higher pressure has more force, it is going to pass through an orifice faster than air at a lower pressure. In order to keep your velocity in check while lowering your operating pressure, you will need to either increase the flow rate or lengthen the time valve is open. To do the first you will need to enlarge the passage and allow the same amount of air to pass through the orifice in the same timeframe. That is the hard way, but the best way. This is because low pressure is a byproduct of efficiency, if you enlarge the orifice and keep the same pressure the ball will have a much higher velocity and you will need to lower the pressure to be within safe limits. The other way to achieve a lower pressure is to lengthen the timeframe the orifice is open and keep the size the same. This will not only lessen your overall rate of fire, but also slaughter your efficiency. To raise your operating pressure you do the exact opposite, shorten the amount of time the valve is open or restrict the flow rate (knowing that is useful to those of you 12-gram fanatics). Also keep in mind that since a higher pressure flows through a given orifice faster, a given regulator’s recharge rate will raise as pressure increases. If that regulator is not designed for use in a low pressure range, it may not recharge fast enough and you may encounter shootdown at high rates of fire.

Now that we’ve got the method of achieving either out of the way, I’ll answer the original question…which one is better. One of the major reasons paintballers believe in low pressure is because they believe it is easier on the ball. Instead of a quick, sharp impact of the air on the ball it is a soft, smooth push on the ball. While logic may suggest this to be true, math tells us that the pressure forced on the ball is generally much less than the pressure your gauge is telling you. Extensive testing by Airgun Designs (AGD) has proved that the pressure behind the ball is nearly always between 65psi and 100psi no matter what the operating pressure is. This means that for your marker to be easier on the ball it needs to operate below 100psi. Most markers require extensive modification to operate at that pressure, and generally for the price you pay the benefit gained is not worth it. For more technical information on this subject you can refer to this site: http://www.thingpaintball.ca/tech.shtml

Another point that is slightly in favor of low pressure is internal wear. Because higher pressures carry more force per unit, they impact an opposing surface harder and slowly wear away at it faster than low pressure. The most common evidence of this is a small patch of silver in your ASA after a long period of use (provided it wasn’t silver to begin with). While it may seem like high pressures will doom your marker forever, it will take an incredibly long time for the pressure difference to wear the marker down. In fact the bolt will wear it’s way through the side of the marker before pressure will damage it. Basically it boils down to higher pressure wearing more on the marker, but not enough to matter.

Up until now I’ve been talking about the pressure directly in front of the valve, but what about markers with a secondary low pressure regulator? Certain applications will give varying results, but this is where low pressure receives most of it’s glory. Most markers with a low pressure regulator employ the use of a ram and hammer assembly. If we recall Newton’s second law of motion, or F=MA, we know that Force is equal to the Mass of a given object times that object’s acceleration. A common complaint about a given marker is the amount of kick the marker generates upon each cycle…this is generally the result of the force generated by the moving mass and it’s acceleration. In order to decrease the force, we need to lower one or both of the factors. We can decrease the moving mass by removing material, or we can decrease the acceleration by lowering the pressure. Now before you go dropping your LPR keep in mind the byproducts of doing so. As stated earlier a higher pressure will increase a regulator’s recharge rate, and lowering your pressure may result in shootdown at high rates of fire depending on just how much mass you are attempting to move. Basically what you want to do is drop the pressure until the marker will cycle at full potential as fast as you can shoot, this is usually around 60psi for most markers, but will still vary from marker to marker.

In conclusion, low pressure does have it’s benefits, but also has it’s consequences. Pressure is just one of the many forces within your marker that influence the way it operates. In the end it simply boils down to what your marker was designed for, because chances are that is the optimum operating pressure. Those of you who are ham fisted tinkerers have probably read over countless articles like these and know what your doing, so I’ll leave you well enough alone?remember, this is just the basics!