It does slightly reduce the sound of the bang, but not by much, its still pretty scary shit when it pops by you and you're not expecting it. My buddy started doing this because he used to use tornadoes and was tired of losing them as they tend to be more pricey than the Thunder B's. Like I said, I don't really use Thunder B's, not my thing, but if you're looking to experiment and making a cheaper alternative to a BB grenade my buddy's trick works well enough. Definitely clear it with a field owner first before using though, should have mentioned that.
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