I guess I’m still missing why this is such great concern you would oppose my statement of ‘buy/build what you want and don’t worry about the second owner’. The M&P sport II isn’t likely fooling anyone already on here. I personally like building stuff I’ll likely never buy another manufacturer assembled ar but it’s because I enjoy tinkering. I also enjoy using premium parts where it counts and using second hand or lower end parts where it’s less important. But those are my preferences, and as mentioned before the likelihood one of my blasters will fail from wear is pretty low. Would I trust them defensively? No more and no less than any other weapon I own with equal trigger time.
If you enjoy building, it would behoove you to watch the podcast posted in the original post.