George Zimmerman Kills One Deal ... Strikes Bigger One for Trayvon Gun

George Zimmerman will now make $100,000 more than anticipated for the sale of the gun he used to kill Trayvon Martin -- because he got a much bigger offer for the 9 mm weapon.

Zimmerman had reached a deal with a Florida bar owner to sell it Friday for $150k -- but at the last minute Zimmerman pulled the plug when he found out someone else was offering $250k.

Sources connected to Zimmerman tell us a female bidder contacted his attorney Thursday to make a deposit. Zimmerman initially didn't take the offer seriously, but we're told her funds were verified before the auction ended.