I have an AR with a 24" barrel that I feel is over gassed. I wanted to see if others have experience with a 24" barrel and what the gas port diameter (not gas block) is on the barrel you have. The port now is .100" which is the same as on my 20" barrels. Does anyone know if there is a standard for a 24" barrel with rifle length gas?
Thanks

Barrels that long with standard rifle gas block location are a problem; the gas comes too early while there is still pressure in the barrel.  The brass is stuck to the chamber walls and in the worst cases the rim can be torn off.  The problem can be partially mitigated by a small gas port or and adjustable gas block, but if you look closely at the brass you'll see bent rims.  The real solution is moving the gas block 2" forward and lengthening the gas tube by the same amount; the port size usually goes larger due to the lower port pressure.  I shoot 28" barrels for NRA High Power & Long Range competition, and have no problems while using the forward location.  My first barrel was 24" with standard rifle gas locations; I could get it to work with an adjustable gas block but it was finicky and my brass suffered.  You can get modified barrels and gas tubes from White Oak Precision (John Holliger), usually from stock.