It is a good thing.
The old Colts used to have a chunk of metal that prevented the installation of an auto sear. What this caused with the need to use the old style "half-moon" Bolt Carrier which used the flange of the firing pin to cock the hammer of the rifle.
Newer Colts use the M-16 carrier that has a "full moon" Bolt Carrier that uses the Bolt Carrier to cock the hammer. The way it was originally designed to work.
You might also want to find out what the serial number range is and make sure it si 60000+. That way you have the mil-spec .154 diameter pins. That way if you want to swap/upgrade trigger components at a later date you don't have to buy special .173 diameter parts.
