Adjustable power Nitro spring idea.

[Laser Eye Jim]

Just kicking around with the idea of making my XL adjustable power. IMHO This rifle really needs something like this. I think a lot of its wild behaviors could be tamed down a bit with matching power vs. pellet. Along with all of the other potential benefits that comes along with adjustable power. Not sure if anybody has done anything like this before but I can't think of any reasons why this wouldn't work.
If anyone has any suggestions I would appreciate some feedback.
I am always dreaming up something new,something different.
The thought of it excites me to no end lol..
Here is a couple rather crude sketches of how something like this would look
It most likely wouldn't work with a rifle with Iron sights as it may be problematic as far as keeping it out of line of sight.
What do you think?

[Privateer]

So that is a bleed off valve kind of thing?

[Laser Eye Jim]

So that is a bleed off valve kind of thing?

Exactly. The drawings are a little vague. But with a finely machined little block with a precision needle inserted, would give one a very precision way to fine tune overall compression within the cylinder. The blow off hole And  needle size would have to be figured out but the bore in the block would not need to be any larger than say1/2 to 3/4 of the diameter at most of the actual breech exchange port. So in essence you would have unlimited variable power at the turn of a knurled screw.
The only thing that may come to question is would the air blowing out cause any unwanted turbulence with the air exiting the transfer and into the barrel behind the pellet..

[oconeedan]

Neat idea.  What if, you used a tiny ball valve instead?  I would think the air flow running around a needle valve would hurt the performance.  But a ball valve, would allow the air to flow through it.
Or, your same set up but instead of a needle valve, that same "needle" with a hole through the center.  Screwing it in out out, you move the hole in and out of line with the transfer port.
Either way, you have to do some major modification.
Dan

[Scotchmo]

That would make for a poor shot cycle. Adding a "leak" to the compression chamber will reduce power. The reduction in pressure will also allow the piston to slam. You have not reduced the spring energy, so that energy has to go somewhere.

oconeedan,
Your idea is a little better. Adding enough "choke" to the transfer port will cause a reduction power, but it will do it by causing piston bounce. Better than slam, but still not good for the shot cycle.

You could combine the two ideas but when implemented, you are left with a low power, hard to cock rifle.

The better way to reduce power is to reduce the spring energy. That will give you lower power AND less cocking force.

Idea -
Replace the stock gas spring with an N-forcer type. They have a valve in the back. Make a custom "tube cover" for the rear of the rifle that has a fill adapter built in. Use a 3mm hex key to release gas and a pump or nitrogen tank to increase the pressure.

[Nate530]

I agree with Scott. Since the ram itself will still move with full power, rapid loss of pressure through an extra relief port in the chamber would cause a violent slam with the piston. The idea of adjustable power comes from shots per fill ratios in PCP. An additional port would not simply allow for shorter air injections down the barrel, without opposite reaction. It is intuitive thinking, but wouldn't put you "in control" of the XL's power. The only possibility would be to find a weaker ram capable of a small amount of preload, so the ram doesn't over extend. Keep thinking and posting new ideas. Creative thinking is awesome. Springers have one setting ,full power or none.