After reading Hamish`s thread in search for more bolt speed on his 175lb rifle I decided to have a go of increasing the speed on my little hand held poelang made pistol by adding an extra 80lb limb rather than increasing the stroke which looks a lot of hard work making the bits .
I cut the ends off a spare limb so it would clear the nocks on the old limb . Drilled a couple of 6mm holes and made a couple of little ptfe pads to dampen any noise between the 2 limbs and work as sliders . The stroke was increased by what ever the thickness of the limb was .
Took about 10 minutes to mod the extra limb .
I chrono`d my pistol when I first got it and got around 180 fps shooting 106.5 grain aluminium bolts. which gave 7.65ftlb of power.
After adding the extra limb it now shot the 106.5 grin bolts at 235 fps for a power of 13 ftlb
It shoots really flat out to 20 yrds now so I`m very pleased . 20 plus shots through it so far and nothing has broken . I might mod the cut limb a touch more at the ends as it looks like over time the edge might damage the string at the loop serving . But then again I might not as strings are cheap and it shoots great so I can live with decreased string life for the extra power gained .