In terms of power Tests 2 and 4 has the launcher powered with two springs to add more distance when launching. The ammo is large foam insulator for the grenade; material that is similar to stefans.
Step-By-Step coming soon!

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For ammo, I used foam pipe insulator (similar to the material for stefans, only bigger.)
I'll try to place a video file later. Can you give me a list of available video formats?