I have found that browsing gun forums gets the best results. this forum, arfcom, m4carbine, and my local gun forum have all had great deals. granted they are sprinkled in between overpriced deals but if you search enough you will find deals. gunbroker also works, alot of people misspell auctions or have retarded headers so their auctions go unnoticed and you can get a good deal that way. gunbot is also a good resource but damn you have to be fast.