Originally Posted by Moral
I have a LP CP reg and when used with the geo I can only get around 260 fps.
uziel's post was pretty thorough, but just to recap you cannot use an LP tank reg on a Geo and achieve the desired FPS. if you are using an LP tank reg then you need to get an LP spring to replace the stock spring on your Geo's HPR. this will allow you to achieve proper FPS w/ an LP tank reg. Be careful not to use an HP tank reg with the LP spring installed as it may potentially damage your Geo's solenoid.
other fix is to replace your LP tank reg with an HP tank reg. i'm not sure about CP reg's but i know certain reg's like guerilla air sells a conversion kit to turn LP into HP, so you might be able to do that.