I purchased my first AR15 3 years ago and finally got to shoot it about 2 months ago. Loved it. Then decided I wanted to build one. My son in law gave me a complete PA10 upper to start. Now I’m finding out the “AR10” platform isn’t as standardized as the AR15.
I’m having difficulty trying to determine which upper I have (gen1,2 or3). Just want to get correct lower. Hoping I can learn some things here