You should learn how antenna works first.
Gold Gun is not metal detector (which is based on near field transmission), so big TX power is here irrelevant (in most cases even destructible to our goal).
Gold Gun is based on (mostly weak) far field signal transmission and should be tuned in adequate way to work properly.
For those interested, I will be honest and post this basic infos again:
http://www.longrangelocators.com/for...8&postcount=14
http://www.longrangelocators.com/for...2&postcount=16