I bought a colt 24" ss barrel ar15 about a year ago and replaced the colt preban lower with an Oly lower (post ban) Only thing is the upper was not colt just a custom job from some one and they put a bayonet lug on it why I dont know ? Ever see a bayonet go over an 1" barrel before? well to make it a post ban can you just grind off the ears that hold the knife in place or do you have to remoove the hole thing ??

 

you can grind the ears but if the barrel is threaded you have to cut the barrel before the threads or screw on a muzzle break and have it welded in place.