Hi guys. First, I would like to thank all of you for your infinite wisdom on all things AR10 and your willingness to explain over and over to people why their rifle won't run when if they had spent a few minutes researching your forum the answer is right there. Over and over again. More often than not it's the wrong buffer tube, too light a buffer, wrong spring and incorrect gas port diameter. What's more amazing to me, when you explain it to them in great detail, they second guess you, do their own thing and ask again what's wrong until ultimately, they do like you said and like the seas parted, problem solved. So, with all of that being said I think i have a handle on it, I think. I do have a couple of problems i need yalls math skills for so there we go.
I am building two different 308 rifles, and everything is going to be the same with the exception of barrel length, handguard/rail length, gas length and triggers.
The upper and lower are both Aero Precision M5's. Barrel #1 is a Criterion M118 Hybrid 18 inch 308 4150 CrMoV Nitride finish with Mid-length gas. It has a .750 gas block journal and I going to be using an Aero adjustable gas block. The gas port is 0.070 and from the center of the port to the end of the barrel at the threads it measures 8 5/16 inches. I am going to run a Midwest Industries 15-inch combat rail and finish the business end off with the Precision Armament M4-72 Severe Duty brake. I'm going to be using a Rise Armament 535 advanced performance drop in trigger. I am running the XH carbine buffer and spring from HeavyBuffers.com that this site recommends. The buffer tube was also purchased from Clint. It's paired to a Magpul PRS Gen3 stock as I plan on this being more of a DMR. I have both am Aero BCG and a CMC BCG but haven't decided yet which to use. Any input there would be appreciated. Barrel #2 is a Ballistic Advantage 12.5-inch 308 Tactical Government Modern Series 4150 CrMoV Nitride finish with Carbine length gas. It has a .750 gas block journal, again using an Aero adjustable gas block. The gas port is 0.063 and from the center of the gas port to the threads at the end of the barrel measures 4.95 inches. Like I said. I really need yalls math skills to figure out what my gas port diameters on both barrels should be, so they run and run all the time. sorry for the length of this but as they say, the devil is in the details. Thank you all in advance.