I prefer free float hand guards on my precision AR guns the pressure exerted on the barrel never changes. With standard hand guards diffrent grips or pressures from diffrent positions can have impacts on accuracy. Free floated hand guards aren't the only piece to the accuracy puzzle but they do help in consistency. the biggest obstacle to accuracy is finding ammo your gun likes. I have a Bushmaster NATO chambered chrome lined mil spec handguard rifle that with most cheap Walmart ammo shoots 2 moa that same gun with Blackhills ammo shoots moa with handloads tuned to it I can squeeze out 3/4 moa.
Best things for accuracy in an AR platform ranked from biggest effect on accuracy to least
1. Ammo
2. Trigger
3. Barrel (non-chrome lined is best)
A. 223 Rem chamber (best for accuracy but SAAMI says not good for NATO pressures. I've shot a lot of it without issue but I'm not an engineer )
B. 223 Wylde chamber (good compromise can run high pressure NATO ammo)
C. 5.56 NATO (worst for accuracy)
4. Free float handguard
5. Locktite barrel extension into upper receiver (there should be no wiggle)
6. Heavy wall upper receiver ( Vltor MUR, Mega Arms SBU, DPMS heavy wall slick side)
7. Squaring front of receiver to barrel extension
8. Clamp on gas block (this is arguable but make sure with free float handguard there is 1/8" clearance all the way around the gas block no matter the style used)
After number 4 maybe number 3 rankings are not really important just things that an accuracy nut is going to care about with the exception of gas block clearance that will screw you if your gas block is hitting the free float handguard.
