# Barrel Extension Mechanisms **URL:** \ **Category:** Proton Packs\ **Created:** [January 23, 2020, 10:31am UTC](https://forum.gbfans.com/t/barrel-extension-mechanisms/10262 "2020-01-23T10:31:23Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![brassgoggles](https://forum.gbfans.com/letter_avatar_proxy/v4/letter/b/a88e57/32.png) [@brassgoggles](https://forum.gbfans.com/u/brassgoggles)\ **Post date:** [January 23, 2020, 10:31am UTC](https://forum.gbfans.com/t/barrel-extension-mechanisms/10262/1 "2020-01-23T10:31:23Z")
Hello! I am looking for as much information as possible on twist-pop and lever based barrel extension mechanisms, many of the threads I can find no longer have working image links sadly. I have a couple of questions if anyone can answer them. mainly, has anyone got any kind of photo or diagram showing how twist pops work?, I just can’t seem to picture it in my head. and in the case of barrel push rod mechanisms I presume RC model parts or something similar are used, is there a generally accepted best array of parts to use for this? ---
**Author:** ![brassgoggles](https://forum.gbfans.com/letter_avatar_proxy/v4/letter/b/a88e57/32.png) [@brassgoggles](https://forum.gbfans.com/u/brassgoggles)\ **Post date:** [January 23, 2020, 10:44am UTC](https://forum.gbfans.com/t/barrel-extension-mechanisms/10262/2 "2020-01-23T10:44:18Z")
(i found venkman69’s build thread with some decent pics of a push rod) ---
**Author:** ![err404](https://forum.gbfans.com/letter_avatar_proxy/v4/letter/e/e9c0ed/32.png) [@err404](https://forum.gbfans.com/u/err404)\ **Post date:** [January 23, 2020, 9:50pm UTC](https://forum.gbfans.com/t/barrel-extension-mechanisms/10262/3 "2020-01-23T21:50:22Z")
From what I have seen the twist pop is nothing more than a spring loaded barrel with a catch that releases when you twist. You manually push the barrel back in to reset. The more complex mechanism is for the thumb lever that can extend and retract.