Bad info, wash. Not gonna work right in his rifle recoil system, brother.
Using the Orange Sprinco spring in a rifle recoil system would be a mistake. You need to research the reason the Orange spring was developed in the first place - hint, it's not for a rifle recoil system, in any way, shape or form. Don't do it.
Upper to lower fit does NOT affect your accuracy, in the least - as long as they mate together and function. Your "accuracy" components are all contained in the upper - barrel to receiver, BCG to locking lugs. The only contact between the upper and lower when firing it the hammer to firing pin, not counting the two pins that hold the rifle together. Your hammer doesn't care if there is a little bit of slop in the mating of the receivers, when it contacts the end of that firing pin...
^^^ Truth. If you're chasing receiver fitment, you're chasing a ghost, as far as accuracy goes.
You can't do that in a .308 AR. AR15 Rifle buffers are 5.900" long, and 308AR rifle buffers are 5.200" long. That shiit just doesn't work.
This is honestly the first time I've read your whole thread all the way through - because you're dealing with PSA stuff. It's my own fault, because I was tired of hearing about PSA problems and issues. I ignore it. What you have/had planned, in what I quoted, won't work. Don't to the Sprinco Orange spring, don't use an AR15 rifle buffer, etc...
Take that for what it's worth... Listen, or don't listen...