Hey Guys, I went shooting the other day with a friend who brought another guy with him. This guy had an AR-15 that he says was a post ban gun. It was a Colt and it had the carbine length barrel and hand guards. It also had a flash hider and a full length non-collapsible rear stock. I asked both of these guys if the gun was pre-ban, they said no, they could tell because the gun was missing the bayonet lug. I am not so sure, can you guys help?
Thanks and take care,
Mark

Flash hider would make it an illegal post-ban. Are you sure it was a flash hider? perhaps a muzzle break that is designed to look like one?

Not having a bayonet lug means absolutely nothing in regards to a Colt rifle being a preban or not. Colt made lots of rifles prior to Sept 1994 without the bayonet lug. Probably conforming to political correctness. These rifles, as long as they have a pistol grip and a flash suppressor are considered grandfathered assault weapons.
In the past 2 years I bought 2 preban Colt rifles from gunstores in my area because they too thought a rifle without a bayo lug wasn't preban and both were bought for less than $800. Both of the ones I bought were as you described, carbines with f/s no bayo lug Sporter Lightweight models.

Only way to know for sure is to contact Colt and ask. If you call customer service they will tell you.