These models were designed by Captain Slug and released into the public domain.
The basic Caliburn 3D-printed Nerf blaster uses a short, wimpy barrel. But if you're a Nerf Chad, slap on the extended barrel for more LENGTH, and then add one of these spacers for protection and GIRTH.
You have two styles - just print one, ya jabroni! MuzzleSpacer has a neat knurled design, and MuzzleSpacer2 extends the endpiece and adds a short segment of rail.
MuzzleSpacer needs three 3/8"-ish 4-40 screws or grub screws to cinch it onto the barrel.
I used these on my Caliburn Sniper in a YouTube video! I actually used them a lot of previous projects, too. Both are nice.