That’s because they weren’t doing it right. As vaguely as I can describe, you need to use a certain caulk you could probably find at say…Home Depot to fix it to the barrel(or machine a metal piece to fix on to the barrel and thread onto the coke bottle). Then you’d remove a measured piece from the end and pack the bottle with a type of insulation commonly found at Home Depot. Anything larger than a .32 will be fairly useless. All of this info can probably be found elsewhere on the internet but of course it’s highly illegal and potentially dangerous, so don’t try this at home. Also I removed a small step so mods please don’t delete this post.