AR rifle buffer questions

[tdbru]

Thank you A5B! i find this very interesting. if i understand the functioning of the Stoner DI gas system, the gas goes down the tube, through the gas key, and into the chamber created by the bcg and the back end of the bolt. once the bcg moves enough to, supposedly, cycle the action, the bolt piston rings uncover the gas vents in the side of bcg as it moves back and the bolt doesn't (yet). so the gas in the chamber is vented out the ejection port. as the bcg comes back far enough, the gas key comes off the end of the gas tube. if at that time, there is still gas pressure in the tube i assume it will get dumped into the action. however, please correct my understanding here, if it is in error, if there is no gas pressure in the gas tube when the bcg backs up far enough for the gas key to uncover the end of the gas tube, no more carbon should be dumped into the action. right? so how can that happen? one way i can see that happening is if the reciprocating mass is high enough that the bullet is long gone out the end of the barrel and all the residual gas pressure behind the bullet and in the tube has relieved itself as is follows the bullet out the muzzle. another way it appears is the oft mentioned adjustable gas block. if the recip mass were infinite, for sure, the gas pressure would be 0 relative to the atmosphere before the bcg moved enough to expose the end of the gas tube. and if the recip mass is "standard" weight, then i assume there's still quite a bit of gas pressure in the tube when the bcg backs up enough to uncover the gas tube. but how much recip mass is required to allow the residual pressure in the gas tube to reach 0 relative before the gas key uncovers the gas tube?? do anyone know Stoner's design equations. mass and spring constant, acceleration, energy loss to unlock the bolt and extract a case, etc? it seems to me that if you throttle the gas, you can indeed reach a point where there was not enough pressure in the chamber to accelerate the bcg enough to complete the cycle. but, if you increase the mass, your bcg accelerates slower, but carries more momentum due to the increase in mass. so might still cycle the action.

just as an experiment, if i find a tungsten buffer, solid, without the hollow, that would weigh quite a bit. it would be interesting to me to see if my rifle would still cycle at all with an increase in recip mass to the max possible. and if it would, shoot 100 rounds and inspect the action for carbon deposits. then do the same thing with the standard issue rifle buffer. and see if there is a difference at all in the amount of carbon in the action. i probably wouldn't want to ask, however, what a solid Tungsten buffer would run.

any mechanical engineers here? or any that would want to chime in?

thanks,
-tdbru