Hey... I have 3 M&P 15 rifles and have never had one single FTF.

I also use Ballistol sometimes, but mostly to flush out a brushed barrel.

Ballistol is a great product, but perhaps not the only thing one should use.

After cleaning, I, and perhaps most, directly oil wear parts with their
favorite gun oil. In limited situations, I use gun greese.

Lots of great helpful stuff out there to understand where and how to apply lubes on an AR.

Stripping and cleaning a new or range used rifle means you have done the right thing to start.
I'd suggest re-trying one of them after applying regular
gun oil.