Board Thread:General Nerf discussion/@comment-32860048-20180529154958/@comment-5276103-20180529231911

Epoxy putty. It serves as a great adhesive, and is also solid enough for a substantial amount of space-filling (not that you'll need very much for a Jolt barrel). Also look into PVC cement at Home Depot for adhesive work; it's great for plastics since it actually chemically melds them together (careful though... it is VERY permanent!). Best of luck in your modding ventures, friend!