The Nailbiter is done - "This Time For Reals" edition. : r/Nerf
Nerf Zombiestrike Nailbiter. Looks to be double action like the Voidcastor with a clip that I would assume ratchets up with every shot. Credits to Alpaca XJ : r/Nerf
NERF Nailbiter Mod Guide (Internals, Spring Upgrade) | Walcom S7 - YouTube