That won't work for a 100fpe 177. It would have to be at lest 2 feet long MINIMUM (give or take) based on that diameter in order for it to be effective.
I hope y'all gathered that the title was a joke. Although in these days of making airguns into something they are not, I guess I wouldn't be surprised if nobody got it.
I made this for my Ataman AP16. I keep it at 6fpe and it actually works. I made it just for practice out of some small scraps I had laying around.