The Sporter has the large pivot pin, and the 6920 has the smaller .25". It all depends on what you are going to do with it. If you want to keep it all original, or if you want to be able to swap out uppers. The Sporter also has different size trigger and hammer pins. If you want versatility and interchangeability with other common parts the 6920 would be the better choice, but if you want to go old school retro, the Sporter.
6530 had fixed stocks I believe? Easy to swap out though and you'd end up with 6520 clone which I would consider to be an ideal configuration.
Any idea what a Colt Sporter HBAR would be worth?
It depends on the condition of the rifle - could be anywhere from $1000 to $1500.



























