I have been very successful with my slingshot rifle Mk2 i made using Barnett slingshot wrist tubing cut at 170mm they stretch to the max flattening 8.5mm lead ball on one side, not sure what the velocity is but i recon its good. Very accurate using a red dot peep sight. I would like to find a supply where Barnett get their tubes from, i did order some Rolyan tubing hoping it was similar but not, thinned walled cut to the same length, cocks fairly easy which show its not as strong as the Barnett type. As you can see in the photo the Rolyan on the left and Barnett on the right. Anyone know where you can get Barnett tubing from or this thicker type, must be from the UK.