Even better, choose between filling your Aspen or Freedom for 20 or 100 full-power shots in the moment, to suit your needs. Before I describe the simple plumbing required, may I explain why I think this will prove a popular mod? Shooting the Aspen exceeded my expectations. However, the pump has proved unreliable. The as-delivered third stage pump head seals failed early. I fixed the gun myself believing that potential repeated failures would take the gun from my hands for weeks, and would cost me a bunch in shipping costs if I went the warranty route. The pump has now failed three times. Without a reliable built-in pump, I'm left with an excellent rifle with just 20 full power shots in the HPA reservoir. I've decided to dump the pump in favor of a bigger air reservoir (or two!).
A note about the 20 shots I get on a fill. Although the gun can be filled to 3600 psi, the sweet spot for consistent velocity is 2800 to 2200 psi. Dialed-in to shoot JSB 18.13 at 900 fps on the high setting, my chronograph records an approximately 12 fps extreme spread for about 18 shots, 2800 to 2200 psi. Many are duplicate velocities given the tiny spread. Add one shot on either end of 18 and you risk a 20 fps extreme spread. Fabulous. No other pressure ranges beat the consistency of 2800 to 2200 fps. More than 2800 psi results in LOWER velocities.
Please see the plumbing diagrams below. Imagine having removed all the pump parts (excluding the big tube that serves as the gun's frame and attaches the front plastic). Those of you who've fixed your guns know how simple deleting those pump parts would be. Now there's a lot of vacant space inside the big frame tube. Having deleted the small pump tube that pushes air into the existing reservoir, we can screw-in any size reservoir we wish. Two interesting choices: Simple larger reservoir or two independent reservoirs.
Option One: Screw-in your chosen-size larger reservoir to give as many shots as you wish (must delete one ball valve - simple job).
Option Two: Screw-in your chosen-size reservoir AND A 2ND FILL PORT (no ball valve delete in this case). This would allow you to take the gun out of storage and quickly fill the original 20 shot reservoir through it's fill-port. Or, you could choose to fill the new larger reservoir by it's own fill-port for many more shots. In this case, the existing ball valves would fill the original reservoir and the new reservoir together. As the pressure drops in the original reservoir while shooting, the already existing ball valves would allow higher pressure air to flow from the new, larger reservoir to the original.
A note about the 2nd option (additional fill port and reservoir): This would require making an opening in the big frame tube for access to the new fill-port. This second option would not allow you to replace the original pump parts without replacing the modded big frame tube. The big frame tube is overbuilt to allow for the torque stress of the built-in pump arm. Personally, I would plan to cut windows in that big frame tube to reduce weight. If the pump parts are removed, and the big tube relieved of excess weight, the Aspen should be lighter by several ounces (and all at the too heavy front end).
I would retain my pump handle, using the existing button to keep it locked closed (other lock down schemes are many).
What do you think? Can this be plumbed with available aftermarket PCP plumbing parts and reservoirs? The simple bigger reservoir should be easily engineered and produced by those that can do such things. See diagrams below. The first diagram shows the original setup. The second diagram shows option two (delete new fill-port and you have option one).
A note about the 20 shots I get on a fill. Although the gun can be filled to 3600 psi, the sweet spot for consistent velocity is 2800 to 2200 psi. Dialed-in to shoot JSB 18.13 at 900 fps on the high setting, my chronograph records an approximately 12 fps extreme spread for about 18 shots, 2800 to 2200 psi. Many are duplicate velocities given the tiny spread. Add one shot on either end of 18 and you risk a 20 fps extreme spread. Fabulous. No other pressure ranges beat the consistency of 2800 to 2200 fps. More than 2800 psi results in LOWER velocities.
Please see the plumbing diagrams below. Imagine having removed all the pump parts (excluding the big tube that serves as the gun's frame and attaches the front plastic). Those of you who've fixed your guns know how simple deleting those pump parts would be. Now there's a lot of vacant space inside the big frame tube. Having deleted the small pump tube that pushes air into the existing reservoir, we can screw-in any size reservoir we wish. Two interesting choices: Simple larger reservoir or two independent reservoirs.
Option One: Screw-in your chosen-size larger reservoir to give as many shots as you wish (must delete one ball valve - simple job).
Option Two: Screw-in your chosen-size reservoir AND A 2ND FILL PORT (no ball valve delete in this case). This would allow you to take the gun out of storage and quickly fill the original 20 shot reservoir through it's fill-port. Or, you could choose to fill the new larger reservoir by it's own fill-port for many more shots. In this case, the existing ball valves would fill the original reservoir and the new reservoir together. As the pressure drops in the original reservoir while shooting, the already existing ball valves would allow higher pressure air to flow from the new, larger reservoir to the original.
A note about the 2nd option (additional fill port and reservoir): This would require making an opening in the big frame tube for access to the new fill-port. This second option would not allow you to replace the original pump parts without replacing the modded big frame tube. The big frame tube is overbuilt to allow for the torque stress of the built-in pump arm. Personally, I would plan to cut windows in that big frame tube to reduce weight. If the pump parts are removed, and the big tube relieved of excess weight, the Aspen should be lighter by several ounces (and all at the too heavy front end).
I would retain my pump handle, using the existing button to keep it locked closed (other lock down schemes are many).
What do you think? Can this be plumbed with available aftermarket PCP plumbing parts and reservoirs? The simple bigger reservoir should be easily engineered and produced by those that can do such things. See diagrams below. The first diagram shows the original setup. The second diagram shows option two (delete new fill-port and you have option one).
