I was considering buying a domain from someone, when a thought struck my mind. If I want to hit the SERPs for a plural, would only having the singular in the domain, affect ranking?

For example, if I bought fungun.com, as opposed to funguns.com, yet I wanted to rank for 'fun guns' in the SERPs. I'm not asking for 'which is best', I'm asking because I can only get hold of the singular for a reasonable price, and so would like to know how badly my rankings would be affected.

Any ideas?