What does a regulator do for a PCP Airgun, and do I need one?
This is a very appropriate question right now as a number of PCP air rifle manufacturers have started offering ‘regulated’ versions of existing models, such as the Ultimate Sporter ‘R’ from Air Arms and the Daystate Regal ‘HR’. For one of these ‘factory’ regulated models the price is generally £100 more than that of a standard model. Of course factory fitted regulators are not new, BSA use one in their R10, Weihrauch in the HW100, Air Arms in the FTP900 and Gallahad (and let’s also not forget the Daystate MTC range of digitally regulated rifles) however these are premium products where the ‘reg’ is a strong selling point, and they are not ‘optional’. There is also a growing offering of ‘after market’ regulators which can be ‘DIY’ retro fitted to many existing PCP models, these start from as little as £60 and are available from Huma and Robert Lane, among others.
So what advantages will I get from a regulated rifle, do I really need one and are they worth the money?
Before we can answer these questions we need to understand how a PCP air rifle works and then what part a regulator plays in improving it’s performance. The workings of a typical PCP are outlined below, I’ve tried to make it as non-techi as possible.
The reservoir is filled with compressed air that wants to get out, but when the valve (red) is closed, it’s way is blocked. The air pressure on the valve presses it against the valve seat and a valve return spring inside the valve body (black) also holds the valve shut.
When the trigger is pulled a striker (hammer) is driven forward by spring pressure and it strikes the end of the valve stem (blue), driving it forward. This opens the valve which allows the pressurized air to escape through the valve body and up into the breech, forcing the pellet down the barrel. The Valve return spring and the pressure in the reservoir then quickly close the valve again, holding it closed until the trigger is pulled again.
When the reservoir is full and the air pressure is high, the more force is exerted on the closed valve. This force is balanced against the size of the valve, the weight of the striker and the strength of the striker spring. This balance is key to the gun delivering constant power output over it’s ‘sweet spot’, even though the pressure in the reservoir decreases as shots are fired. When the air pressure is high, the valve opens for a shorter time (due to the greater force trying to close it) but the higher pressure forces more air through the valve. Then after some shots have been fired and the air pressure in the reservoir drops, the valve will remain open longer (as the force acting on it has now lessened) allowing a greater length of time for air (at lower pressure) to flow through. This results in the nearly same volume of air flowing through the valve in both circumstances. The exception for this is when the air pressure in the reservoir is above the optimum range for which the valve was designed (not the maximum fill pressure) as the valve closes before all the air needed for the shot can get out, or when there is insufficient pressure left in the reservoir.
Nearly all PCP’s will have a performance curve similar to this one, which results in lower POI (point of impact) before and after the ‘sweet spot’
So what does a regulator do?
A regulator is a small device that sits in the reservoir in front of the firing valve and it regulates the air pressure going in to the valve when the trigger is pulled. It allows high-pressure air to flow into a small chamber (firing chamber) until the pressure reaches a certain level, it then closes the chamber to the reservoir. When the trigger is pulled and the firing valve opens, it releases the air from the firing chamber at the optimum pressure to suit the way the firing cycle has been tuned. As the pressure going through the valve is always the same, a PCP with a regulator shoots the pellet at a very consistent velocity and therefore produces a constant POI, as long as there’s enough pressure left in the reservoir. When the reservoir pressure drops below the pressure that the regulator is set to work at the regulator just remains open and the gun then becomes unregulated. At this point the gun will continue to fire, although most shooters notice a change in the discharge sound when their gun is ‘off reg.’ Another added bonus is, as a regulator is more air efficient in the firing cycle (and in some cases they allow guns to be filled to a greater pressure) they will deliver a greater amount of shots per fill.
There are various, differing regulator designs but in essence, they all do the same thing which is they will flatten out a PCP power curve.
So now we know what a regulator does the question is do you need one? and are they worth the money?
Well firstly let’s not confuse ‘need’ with ‘want’. If you are the kind of person that desires precision, wants the best, money no object, then why not. The only down side to having a regulated rifle is that servicing requires greater skill an there is a slightly greater risk of failure, not because they are unreliable, just because there is more to go wrong.
If however you only want to spend what you need to then a regulated rifle will not help you shoot more rabbits, or massively benefit you at the plinking range (unless you want to spend slightly less time filling you air rifle). You may well consider it a necessity though or money well spent if you’re competing in HFT (hunter field target) or FT (Field Target) where you need to rely on the consistency of your set up.
Factory fit v Retro fit
As mentioned at the start there are several companies which specialist in the manufacturing of regulators, such as, Huma and Robert Lane. You can buy directly from both, a regulator designed specifically for a given rifle which will be set accordingly to a certain pressure. Depending on your skill / bravery / available equipment and time you then can install these yourself and you will definitely get a performance lift in consistency but maybe a slight drop in power, however in our experience fitting the reg is only part of the job. To release its full potential the whole firing cycle needs to be balanced and in many cases internals (valve, spring etc) need to be modified or changed . As every rifle is slightly different this is a job that needs knowledge and experience to accomplish, and there are plenty of experts in this field, we use Dave Wellam (Airmasters) but XTX Air also have a good reputation. If you’re DIY fitting you will require access to a reliable chronograph to ensure you comply with the law.
So all things considered a factory fitted regulator that will be individually tuned and supplied with a warranty for £100 seems like excellent value. The new Air Arms Ultimate Sporter ‘R’ for example. The regulator takes an already fantastic rifle to another level, so why compromise.