This is a modification to the muzzle for Captain Slug's Rivalburn 3. The original design called for a screw driven in to the top of the muzzle to act as a hop up. I found this to lead to slightly inconsistent hop up. I also was worried about the edge of the screw causing excessive wear on my rival rounds, so I designed this.

This design makes two small changes to the standard Rivalburn 3 muzzle. The first is obviously the slot to install the hop up. The second change I made was to open up the hole after the barrel ever so slightly to make the round less likely to skim one of the edges and pick up side spin.

You will need to print the R15_Muzzle_modified.stl and the hop up of your choice. Hop up 1 produces the least hop up, while hop up 4 produces the most. I found hop up 2 works best for me, but use what you like.

The hop up is installed by pressing it in to the muzzle before installing the threaded rod through the top of the muzzle. These parts produced a pretty snug fit for me.

Anycubic

All-metal Mega

No

Yes

0.2

20%

Print settings and material are up to you, although you will probable need supports. Adjust your support settings so there are only supports in the area where the hop up will be installed. None of the other areas need support.