After fiddling around with various AR things, I have a question that I've been struggling with in some way before and have not much idea how to answer.
What's the deal with bolt carrier gas vent ports?
Why two of them? I pin-gaged the three BCs I own, my Chinese AR measured .111" diameter on both holes, the Canadian NEA at .106", and the US-made LMT at .108" diameter.
Why that size (taking into account relative barrel gas port size)? Why not smaller holes (requiring less gas from the port in the barrel, therefore requiring a smaller port in the barrel)? Smaller holes on both ends would probably have less gassing when using a muffler, as there's less gas in the system in the first place. Why not larger on both sides (larger barrel port and larger carrier ports)? More gas might be less sensitive to ammunition variance or something.
I've talked about this to my engineer uncle, he said it was indeed a fairly complicated issue as the system does rely on gas pressure so you have a lot of pressure differentials that affect each other. Did Eugene and his team math it out or did they try it out in various configurations in trial-error?
tl;dr what are the design considerations of the carrier-to-gas-block port sizing?
In an LR-300, where the gas key doesn't separate from the gas tube, would the design considerations of carrier-to-block port size change? I remember seeing the LR-300 having more gas ports on the carrier; this makes sense if the gas block port sizes are the same as a similarly set-up AR-15.