Hey, I bought a stripped lower for almost $150 and when I tried to build it discovered it was out of spec..it works but it's now a dedicated pistol lower I never shoot.
Commercial vs Mil? I learned that the hard way too. I also bought a stripped lower for $100 something a couple years ago, went to hammer the pin on the trigger guard, hit my thumb, screamed $#@% then hit the lower just right to make it completely unusable! It's now hanging in my shop as a reminder for me to NOT lose my temper LOL