Here's my steampunk Slingfire. worker short dart conversion kit with full metal internals. one of my custom scar barrels. 9kg spring. hits around 130fps. : r/Nerf
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Here is the Monarch, a 150fps Slingfire integration. Full specs and links in comments. : r/Nerf
MaLiang 3D Shotgun Barrel Muzzle Sight for Nerf SlingFire | AK Blaster MOD
NERF Slingfire Custom Paint by ArdisFoxx on DeviantArt