Diana is a well-known name in air rifle circles. Diana has been making air rifles for over a century and the company can trace its origins back to 1890. Their history is one of innovation and new ideas. Diana is still doing that, as demonstrated by the new Stormrider PCP air rifle. The Stormrider brings the PCP air rifle in at a budget-appealing price, and quality, that is sure to win over a whole new generation of shooters. Nioa is the Australian agent for Diana and gave the SSAA Australian Shooter/Hunter the opportunity to review this product in .22 calibre.
Pre-charged pneumatic (PCP) air rifles have much to commend them. Being of compressed air design, rather than the conventional spring-powered type, PCP air rifles offer high velocities and excellent accuracy. They also need to have a suitable pump, or a scuba tank with the appropriate fittings, to charge their pressure cylinder. Up until now, the higher cost of PCP air rifles and the extra cost of pumps or scuba tanks has deterred a lot of shooters. Diana’s Stormrider PCP air rifle and the provision of a suitable 3-stage manual pump, both at affordable pricing, has greatly reduced the price hurdle for folks wishing to shoot PCP.
Straight out of the box my initial impressions were of its compact and lightweight build. Being a PCP air rifle, I had expected something larger and heavier. At a glance, the design looked uncomplicated and build quality appeared good. I liked the balance and feel of the rifle. Unlike a lot of other PCP air rifles, the Stormrider comes with open sights, so you do not have to invest in a scope if that suits you. Overall length is 900mm (with the suppressor removed to meet Australian law). It weighs 2.2 kilograms. The barrel length is 490mm. The rifle is rated to an energy of 26 foot-pounds or 35 Joules.
The Stormrider is a bolt-action repeater with unregulated PCP propulsion. That means, unlike a regulated PCP action, the compressed air released to shoot the pellet out of the barrel is not regulated to a constant pressure. As the air in the reservoir is consumed, the pressure available drops off a smidge with each shot. This can affect accuracy once the pressure in the reservoir drops too low. I tested this, and the data is illustrated in the accompanying graphs, but more on that later.
The .22 calibre magazine holds 7 pellets while the .177 model holds 9. The small rotary magazine clicks into location with a magnetic latch. Alternately, a small, grooved tray allows easy single-shot loading. The single shot tray is likewise clicked into place with a magnetic latch and, while firmly positioned, is easy to fit and remove.
The rotary magazine requires that the first pellet is loaded skirt-first. This holds the rotary spring and the remaining pellets can be loaded head-first from the other side.
The Trigger and Safety
The Stormrider trigger is not adjustable. You would not expect that on a budget-priced model anyway. That said, the trigger is fine. It has a consistent weight of pull around 2.6 pounds, which is ideal for a hunting and plinking rifle. It has a little creep, not always a bad thing and gives a signal for the breakpoint for the shot.
The safety is of the manual cross-bolt type. There is a clearly visible red indicator for the Fire position. The safety clicks between safe and fire with a distinct and positive click.
Compressed Air Reservoir
The Stormrider reservoir holds 100 ml of air. That is sufficient for up to 30 shots, being aware of the power curve of this unregulated PCP. While that may limit your shooting on one charge of air, I see that as a positive. The smaller reservoir contributes greatly to the compact size and light weight of the rifle. Also, when using the manual pressure pump, the smaller reservoir requires much less pumping than the large reservoirs on some PCP rifles. Once you have pumped up any PCP a couple of times, you will appreciate that fact. Under the stock, a pressure gauge is set back out of harm’s way. That tells you the remaining pressure in the reservoir and a good habit to develop with PCP shooting is to regularly check that. Another benefit of the smaller reservoir is that given the size and pricing of this air rifle, I can see it being used a starter and training rifle for youngsters (under supervision of course). Having to refill the reservoir at some personal effort, is a great moderator and instils the value of making every shot count.
The biggest hurdle to PCP shooting is charging the rifle reservoir. This has to be done either by a special manual pump or from a scuba diving bottle. PCP air rifles operate at very high compressed air pressure, way higher than your shed handyman compressor. Diana produces a 3-stage manual pump with a water-cooled jacket specific to the task. The pump has folding foot-rests, pressure gauge, 1/8″ BSP quick fill adapter and a spare part set included in the carry bag. This pump retails for about $225.
A second-hand scuba tank and an appropriate filling connection will cost at least $500. You will get a lot of refills of your PCP from a scuba tank. Once the scuba tank pressure drops below 150 bar pressure, it will need to be re-filled by a dive shop. That will cost about $10 and, additionally, the bottle will need to be certified, at a cost of about $20, every year. However, if you get right into your PCP shooting, a scuba tank offers great convenience.
A PCP air rifle like this is at its best with a scope. Nioa provided a good choice of optics with a Leupold VX-Freedom 3-9×33 EFR (#175075) featuring the fine duplex reticle. Most important is the adjustable parallax down to 10 metres or so. This allows the utmost accuracy to be extracted from the rifle by adjusting the parallax to air rifle ranges. Being a mild-mannered PCP air rifle, there is less to consider in the choice of scope. The PCP has minimal recoil and is kind to its optics.
I used Sportsmatch high mounts to give me room to manipulate the rotary magazine in and out of the action. I also slide the rear open sight off its dovetail fitting to ensure clearance for the scope.
Off the Bench
Air rifles are not unlike their centrefire counterparts in that some ammunition shoots very well while others do not. It always pays to test a variety of ammunition to see what your rifle prefers. I put the Stormrider through its paces over a chronograph and shot groups from a range of pellet types. The results of that are summarised in the accompanying table.
Small game and pest hunting are primary uses for air rifles. I therefore settled on the H&N Baracuda Hunter 18.2 grain hollow-point pellet for further testwork. This pellet shoots nicely in my other air rifles and gives the best expansion of any pellet I have so far tested. It hits rabbits and Mynah birds hard and ensures humane kills.
The PCP Pressure Curve and Sweet Spot
Unregulated PCP air rifles demonstrate a variation in muzzle velocity as the reservoir cylinder loses pressure. To determine that for the Diana Stormrider, I pumped the reservoir up to 190 bar and began shooting 3-shot groups with the H&N Barracudas. The results of this are shown in the graphs. I had expected to see a steady decline in measured velocity and was therefore surprised to see a peak in velocity before it began to decline as expected. Thinking I had a problem, I did some Googling and discovered that is normal behaviour.
The graphs show the decline in reservoir pressure (3.3 bar per shot fired) and the resultant impact on muzzle velocity and accuracy. In terms of optimal accuracy there is a clear “sweet spot”, the green zone on the graphs. To extract the best accuracy from the Stormrider, it would pay to make sure you maintain the reservoir pressure in the 100 to 140 bar region. It should be noted that at pressures below 100 bar the point of impact starts to drift while accuracy remains good.
That turns out to be a very convenient pressure zone. Using the 3-stage hand pump, it is quite easy to pump the reservoir up from 100 to 140 bar. The amount of pumping effort required to get from 140 to 200 bar is a lot more. As you can see from the pressure curves, there is no benefit at all in pumping up to 200 bar.
The trajectory will change, taking the point of impact with it, as the muzzle velocity drops off. This is shown in the trajectory plot. With all this in mind, a good recipe for the Diana Stormrider would be to pump it up to 140 bar and, after 15 shots, pump it back up to 140 bar again. That will optimise the consistent accuracy of the rifle. The other point to note is that the point-blank range of the rifle would be best kept to 30 metres to account for the variation in trajectory. If, on the other hand, you keep the pressure close to 140 bar with more regular top-ups, then the point-blank range is out to nearly 50 metres.
With a retail price starting at about $335, and an additional $225 for the pressure pump, the Diana Stormrider presents an attractive entry point into PCP shooting. It will be a great vehicle for practising shooting technique. Compact and lightweight, it will have particular appeal to shooters of smaller stature, and youngsters. With 24 foot-pounds of energy and good accuracy, this an ideal rifle for discreetly rolling rabbits and pests around farmhouses. Diana’s Stormrider is going to bring a lot more shooters into the PCP ranks, for sure.