Don't give up entirely. If you search you may even find an old Colt upper if yours has the two different pin diameters. That bushing isn't as bad as I meant it to be. Other then those pins everything else is 100% interchangeable. Thing is with an old Colt upper, should you find one, is that it will have a handle on it and more difficult to mount a scope, whereas the new ones are flat tops. That's not to say you can't put a good scope mount on the handle. I think you'd get a kick out of an AR15 that KICKS!!! LOL I don't want to discourage you, lifes short, enjoy it.