Snowpeak Snowpeak / Artemis PP800R - How to reduce FPS?

[orangecat32]

I recently picked up an .177 Artemis PP800R, because it is supposed to be regulated versus the unregulated Diana Bandit.

When I shot it with Crosman 7.4gr pellets, I'm getting about 6-7 shots at around ~800 fps consistently, but then after that the pressure gauge hits yellow (100 bar) and then the FPS decreases linearly until about shot 21, when there isn't enough air to push the pellet out the barrel.

I already tried tuning the built in regulator setting by taking off the pressure gauge and turning the screw clockwise, but if I turn it too far down, the gun will stop working entirely (seems like the regulator valve will close off completely if screwed in too far). So the lowest FPS i'm able to tune it to is 750 PSI before it stops working. This leaves me around 8 shots at 750 fps, and 23-24 shots before running out of air.

My goal is fps ~450-500 fps, that way I can shoot indoors without it being too loud, and hopefully get a lot more than just 7-8 shots.

How do I further reduce the FPS? I'm thinking of cutting coils off the hammer spring, but how do I make sure I don't accidentally go too far? Are there replacement parts like a different regulator valve that will bring me closer to 500 fps? Or a tighter transfer port?

Thanks in advance, graph from my testing is below, gaps are from chronograph no-reads

 

[nobody1]

You need a weaker hammer spring.
For a regulated airgun a weaker hammer spring is the easiest way to detune.

I have the Diana Bandit .177 which is unregulated and very hard to tune.

With the Diana Bandit I now get 470-530 FPS with 7.5 grain pellets for 36 shots (4 magazines).
I start at 2500-2600 PSI and end at 1000-1100 PSI.

The thing that helped the most was a 3D printed transfer port from TPU.
The 3D printed transfer port restricted the air flow which flattened the shot string.
This was trial and error until I got to the velocity I wanted.

I have also changed the hammer spring to a stiffer one.

 

[orangecat32]

You need a weaker hammer spring.
For a regulated airgun a weaker hammer spring is the easiest way to detune.

I have the Diana Bandit .177 which is unregulated and very hard to tune.

With the Diana Bandit I now get 470-530 FPS with 7.5 grain pellets for 36 shots (4 magazines).
I start at 2500-2600 PSI and end at 1000-1100 PSI.

The thing that helped the most was a 3D printed transfer port from TPU.
The 3D printed transfer port restricted the air flow which flattened the shot string.
This was trial and error until I got to the velocity I wanted.

I have also changed the hammer spring to a stiffer one.

Since my PP800R is regulated and appears to be keeping a consistent velocity plateau at the first part, will I need a restricted transfer port?
Also, where can I pick up one a smaller transfer port, or is there a 3D printing file I can use?

Seems like a good first step is to clip the hammer spring shorter, I just haven't done so yet without asking first because I don't know where to pick up a spare if I make it too short

 

[Mike_Lenardon]

I was purchased a lighter hammer spring before I cut the stock one.