My favourite K'nex guns of all time are the Mepain's Knexsayer and KillerK's (Knex Lego Maniac) TR8. The TR8 for it's awesome performance and reliability, and the Knexsayer for it's under barrel pump and badassery.
I wanted to combine these 2 aspects in to one gun, which I named the (Me)PainKiller(K). It uses the tried and tested turret and front end mech from the TR8, with the frame and an updated trigger from the Knexsayer. I also removed the stock so I feel like Arnie (see pic), but it's personal preference.
The main reason I did this is I always had problems with the mech from the original knexsayer when adding a lot of bands. The knexsayer has a large distance between the pump and ram rod (see pics) which induces a lot of stress on the pump mechanism.
Credit goes to the original authors, as well as Loyamann123 for bringing the instructions for the Knexsayer to instructables! The idea of adding the TR-18 turret to the knexsayer also inspired this project.
Links to original guns:
Step 1: Front Brick
Front end Brick. Important to get this right. Start from the middle then build the sides.
Step 2: Turret, Pump, Trigger Mech
Pump and turret from TR-8. Trigger mech slightly modified from Knexsayer.
Step 3: Handle and Side Panels
Side panels and Handle are very close to original Knexsayer. See Loyamann's Tr Sayer for detailed instructions!
Step 4: Assembly and Band Placement
Let me know what you think of the gun if you build it!
Thanks to Killerk, Mepain and Loyamann123 once again!