ok before im bolting this thing together ive got a colt upper marked ch w/forward assist no deflector...no more marks anywhere .built in cary handle...can i put my mega lower on this upper...pre ban/ post ban...any help please ..also installed a 20" bull barrell post ban from mod 1 sales  ..input please...mike.

Post ban lower with post ban barrel, your good to go. When the actual upper receiver was made doesn't matter, just the barrel configuration

Why is this?  Whats the difference between the Pre&Post barrels or lowers?

In 1994, Willie "The Cigar Man" Clinton, decided to pass legislation making assault weapons illegal to manufacture unless they were for law enforcement or military use.  Any weapon that was already an AW before the law was grandfathered in.  So, a lower receiver off of one of these pre-ban AW's can still be used to make what meets the definition of an AW.  According to the legislation, an Assault Weapon is defined as a rifle that is capable of using a high capacity magazine (greater than 10 rounds) and has more than one of the following evil features: 1) collapsible or folding stock, 2) pistol grip, 3) bayo lug, 4) flash suppressor or threaded to accept a flash suppressor, or 5) grenade launcher.  So, if you have a post-ban lower receiver (one that was made after 1994) you have to use a barrel that does not have a bayo lug or flash suppressor.  Since the AR15 has a pistol grip, that is the one feature you are allowed to have.  So, no collapsible stock, no bayo lug, no flash suppressor, and no grenade launcher.  If I left anything out, my esteemed colleagues will fill in the blanks.  

Charles Tatum
Alamo Professional Arms

hey thanks for answering me....im not spooked now...but i went to order my bolt and carrier ass...at sturms guns and they wanted to see my gun....they freaked out on me....told allegal conf....and to take it apart because of a1 sight base and old colt upper....no bayo lug. or threads on barrell....piss on em  they wouldnt sell me any parts....oh well...plenty of mfgs on internet   mike out..

They are absolutely full of ummmm, birdseed; yeah that's right, birdseed.  The upper configuration has absolutely nothing to do with post ban requirements.

Incidentally, have you made sure that uor Colt upper has the small. push pin type, hole in the front.  Colt did make some commercial large pin forward assist uppers for awhile.  

If it should turn out to have the large pin, I'd advertise it for sale on the site here.  There are several guys hunting large pin A1 forward assist uppers.

Not me tho. Got mine last year[:D]