Yeah, grenades are pretty much useless outdoors unless you are on a field with a lot of buildings and bunkers, which are rather rare. Inside in CQB there's only one grenade you need, the Tornado Impact (by Airsoft Innovation, a Canadian company). Their timer grenades are sometimes finicky, but the Impact work perfectly every time. They throw 200 BBs around, are super safe and sound wise they are not dangerous for the ears. They use propane, and you don't have to buy shells every use. They are basically infinite re-use. They are also accepted everywhere, I have never ever seen a game that doesn't accept tornadoes.
Keep quiet. Sound travels faster than BBs.
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