It didn't work fine - you didn't know enough about the recoil and gas systems to know any better. You were beating your parts up, causing unnecessary wear and tear, and didn't even know it - bet it kicked like a mule, too.
We have ALOT of PSA data here. A metric shiit-ton of it. And the fixes.
Your PSA worked, for as long as you shot it, with a buffer that was too light, probably had an AR15 carbine recoil spring in it, the gas tube was too short, and the gas port was too small. But it shot, for you, and you thought it was just fine. If you had an early one, I'll bet there are marks on your lower receiver, where the BCG was slamming into it. When you talk to your brother that you sold it to, tell him to send you pics of that area, and post them here.