List and/or describe proven improvements that are better than mil-spec. This not a list of items that people just like better but upgrades that actually improve the function and/or use of the AR/M4 platform

For example: (short list)

1. Medium contour barrels- better balance, harmonics, distributes heat more evenly

2. Ambidextrous charging handles- better manipulation characteristics

3. Triggers- accuracy

4. Free float hand guards- accuracy

5. Pistol grips- better grip angle

6. A5 Buffer System- enhances function


Also would like to discuss nitride. Not sure if nitride is better than phosphate for barrels and BCG's but starting to lean towards nitride as having better corrosion, ware, and added lubricity characteristics.