Not necessarily get bigger, but it is like a bell to ring. That range it can ring depends on how many participants joined your bounty. You can just simply advertise in other site and people can still be aware of your project without them needing to be in the forum but the reason why most bounties as an advertisement are being done here is because most of the members here are aware, if not knowledgeable, to cryptos. Investors would be aware of the project you're trying to impose. Telegram is just necessary for the sake of the community of your investors, not typically a way to make your project bigger.