Air Venturi Seneca Aspen Part 1
The PCP air rifle that goes it alone
By Dennis Adler
Dedicated air rifle hunters and competitive shooters know that PCP stands for Precharged Pneumatic. And that means superior velocity and accuracy for hunting small game or precision target shooting. A PCP is capable of much more than 12 gram CO2-powered air rifles or even those with larger 88 gram CO2 cylinders. A PCP also allows sustained firepower while traditional single shot break barrel spring piston, gas piston, or pump guns only allow one shot. This is a topic I have not spent any time writing about in Airgun Experience because this column is more focused on handguns than rifles, and always on guns that are self contained. Simply, precharged means you must have a source to put air (not CO2) in the rifle or pistol’s reservoir. This is traditionally done with either a compressor or a scuba tank. It can also be done, quite laboriously, with specially designed hand pumps, which is the only way to make a precharged pneumatic air rifle portable enough for use in the field away from any lightweight means of recharging the air supply. The hand pump is actually a very old solution because precharged pneumatic air rifles were developed in the late 18th century!
Forging the trail West
During their 1803 to 1806 Corps of Discovery Expedition from St. Louis to the Pacific Coast, Lewis & Clark carried a version of the Austrian Girandoni air rifle, which was manufactured for Meriwether Lewis in the Philadelphia shop of gunsmiths Seneca and Isiah Lukens. The Austrian-built, rifled barrel, .46 caliber Girandoni, upon which the Lukens design was based (and it may have been a Girandoni), were actually carried by the Austrian Army from 1780 until the early 1800s, instead of conventional flintlock muskets. The Girandoni were powerful, effective at long range, easy to fire and capable of multiple shots. Except for the air reservoir inside the shoulder stock and a distinctly different sound when fired and absence of smoke and muzzle flash, they looked very much like a flintlock musket. The hard part was filling the Girandoni’s air reservoir which required some 1,500 strokes with a hand pump to fill it to around 800 psi. This provided the Girandoni with enough of the ethereal puissance to discharge a total of 22 rounds; 21 of which were contained within a tubular, gravity fed magazine, plus one chambered round. The advantages of this gun compared to a musket quickly reveal themselves. And a Girandoni could send its round lead ball downrange at velocities of 750 to 950 fps, still an impressive velocity for a large caliber air rifle over 200 years later. They were, unfortunately, very expensive to manufacture. Other similar air rifles were manufactured in Germany in the early 1800s, Mortimer in London, built a repeating air rifle around 1815 and Stormer in Herzberg, Germany, produced a Girandoni-design air rifle between 1820 and 1830.
Throughout most of the 20th century, less complicated single shot pump air rifles, spring piston and gas piston break barrels were preferable, and much easier to manufacture than the ancient Austrian and German guns. Modern air rifles, however, had to suffice with much smaller calibers, .177 or .22 for the most part. Then history began to repeat itself with modern precharged pneumatics in the late 20th century. Again very expensive compared to more conventional air rifles, the precharged pneumatics became the choice of air rifle hunters, target shooters, and Olympic air rifle and air pistol competitors. And unlike the Girandoni, all that is required to fill the air reservoir of a PCP rifle (or pistol) is a compressor (or small scuba tank designed for precharged pneumatics). Of course, if you scroll through the PCP rifles sold by Pyramyd Air you will also see that special hand pumps are made today as well, making some precharged pneumatics suitable for hunting in the field. This is another area I generally do not write about. But the Air Venturi Seneca Aspen gave me a reason to reconsider. While it can be filled with a compressor, it doesn’t need one. And it doesn’t need a hand pump, either. In fact, it doesn’t need anything to refill the air reservoir, other than the person using it. The Aspen has its own built-in pump.
This is not the same as pumping air into a pneumatic pump gun, which generally uses one pump (some are multi-pump) to achieve sufficient air pressure for a single shot, this is pumping enough air into the reservoir for multiple shots like the ancient Girandoni. The Aspen also has the advantage of either firing a single shot, using a removable pellet tray, which perfectly aligns the pellet at the breech as the bolt closes, or a 10-round rotary magazine that fits into the same slot and is rotated by each cycle of the bolt action. This design is similar to the Diana Chaser 4.5mm (.177) or 5.5mm (.22 caliber) CO2 Pistol/Rifle sets I wrote about in Airgun Experience last August, and that is what drew me to reviewing the Aspen. For someone who looks at air rifles from the perspective of simplicity of use, i.e., insert CO2, load and shoot, or even more simplistically, ready the gun for a single shot with a side lever, under lever or break barrel action, the Aspen offers a perfect compromise between traditional air rifles and precharged pneumatics.
The 10-shot (.177 and .22 caliber) magazine design for the Aspen resembles the Benjamin Marauder rifle magazines, as well as the Umarex Gauntlet, and Kral magazines, but with these PCP models you have to fill the air reservoir with a compressor (or a hand pump). The big advantage to the Aspen is that this precharged pneumatic can go into the woods with you and requires nothing else in tow to keep shooting, but pellets.
How it works
The Aspen can be filled with a compressor like any other PCP and there is a large pressure gauge that reads in both psi and bar on the right side of the receiver. There is a connector under the receiver that allows attaching a compressor to fill the 3600 psi air reservoir. But the Aspen also has a large lever under the receiver that looks like a modernized lever action rifle, only this lever is not used for chambering a round, but rather manually charging the air reservoir. This is the only PCP air rifle with this unusual feature. The lever is securely locked in place by a large crossbolt safety. When locked, the lever provides an easy means for carrying the Aspen, which is no lightweight, and the extra width of the lever also provide a flat rest for the support hand when shooting.
Maximum recommended psi for the Aspen is 3600 (actually 3626 psi but the pressure gauge redlines at 3600). What you will ultimately discover is that there is very little reason to pump it up to 3600 psi. At somewhere between 2500 and 3000 psi you will find the combination that will deliver the best consistent performance with most .22 caliber pellets. It took me 90 strokes to get the pressure up to 2800 psi. I know, that’s a lot of pumps in a row, but the Aspen’s pump handle is not that hard to work; it takes a bit of effort but a slow, steady motion to open and close each time is more tedious than laborious. Once you have psi up to where you want to start, and begin shooting, you can watch the gauge, which is oriented to be easily read by leaning the rifle inward. (Looking at it from the side the gauge is almost upside down, but it makes sense when the rifle is in your hands). After firing a few rounds, you can stop and pump it back up to the desired pressure with only four or five strokes. As for running it out, that’s not necessary for short term use, and for long term storage the gun has a depressurizing screw and a separate wrench to loosen the screw and allow remaining pressurized air in the reservoir to escape. (Make sure there is no pellet chambered as depressurizing could send it downrange). Afterward, tighten the screw and the gauge should read zero.
For all intents, the Aspen looks and feels like a tactical rifle in the hands, and tactical is not a bad description, either. It is a fairly large gun with an overall length of 43.3 inches, and a carry weight of 8 pounds. The stock has front and rear sling swivels; the contours of the rifle are trim and shaped for a solid grip and cheek weld. The gun has a very deep stock and a large, 3-inch circumference barrel shroud. The top of the handsomely machined, black anodized receiver is drilled and tapped and the integral 11mm rail will accept a variety of scope rings for optics. The Aspen has no sights but you don’t need to decide on a scope right away as it comes with its own 4x32AO rifle scope and rings. And the MSRP for all this is an impressive $399, about $100 less than a Benjamin Marauder model and equal to the Umarex Gauntlet (with scope), but neither of those have the capability to recharge their own air supply; that puts the Aspen in a class of its own and the number one reason to take this gun on a hunting trip. It is also almost silent, except for a brief, sharp metallic ping. Compared to a .22 Long Rifle with a noise suppressor the Aspen is still quieter, yet it can send a lightweight .22 caliber pellet downrange at over 900 fps.
In Part 2 we start working up psi and pellet combinations.