It works, BUT:
1) You need to stay with low-velocity ammo, like the .22 short, .22 long, or .25ACP
2) It's only good for one shot. A bottle with a gaping hole in it won't contain the hot gasses generated and cool them down. A second shot will require a second bottle.
It's REALLY, REALLY not worth the hassle, and not worth the risk of getting arrested for illegally manufacturing a silencer!