AR rifle buffer questions

[A5BLASTER]

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

The gas tube is going to have pressure on it until about the time the case is flying out the ejection port.

You don't have to add weight to the bcg. Your going to find out real quick when you start dropping tungsten weights into the buffer just how far you can go before the rifle stops working due to not having enough gas to unlock and move the weight of the bcg and buffer.

The only true way to reduce carbon fouling in the action is by reducing the amount of gas needed to run the system. The only way to reduce the amount of gas getting to the bcg/gas key/ gas rings, is by choking it at the gas port vie a adjustable gas block.

[A5BLASTER]

Here is a experiment you can try.

Clean the action and bcg squeaky clean. Then move your gas block so zero gas can go down the gas tube. Fire 5 rounds, running the bcg by hand vie the charging handle.

Then put the gas block back in place and drop a h3 carbine buffer in your rifle and fire 5 rounds.

That will show you very quickly that the only way to cut down how dirty the incoming gas makes the action is by choking down the amount of incoming gas.

[tdbru]

Thanks again A5B! this i can give a try. question though, why an H3 carbine buffer and not the rifle buffer that is in it? curious. and if i remove the gas block, then of course no gas gets into the action. it should stay clean. are you really suggesting comparing a rifle buffer vs a carbine buffer in terms of recip mass and see the difference? sorry if i'm a bit slow on the uptake.
-tdbru

[A5BLASTER]

Thanks again A5B! this i can give a try. question though, why an H3 carbine buffer and not the rifle buffer that is in it? curious. and if i remove the gas block, then of course no gas gets into the action. it should stay clean. are you really suggesting comparing a rifle buffer vs a carbine buffer in terms of recip mass and see the difference? sorry if i'm a bit slow on the uptake.
-tdbru

Sorry forgot it was a rifle buffer. You can buy heavy rifle buffers. Are you can change out the weights with tungsten weights and then try the experiment I posted above.

What you will see is as you add the weight to the rifle buffer, the felt recoil will smooth out, but the gun will still run just as dirty. Then as the weight reaches a point of to much the gun will start short stroking, undergassed issues. Then if you continue to add weight the problem will worsen till the bolt doesn't unlock anymore.

So you see when again come full circle, the only way to lower the amount of crude getting into the action is to choke back the gas at the gas port.

I have run my grendels with carbine and rifle gas setups with everything from standard gas blocks and heavy buffers and extra power buffer springs.

To the very far opposite with adjustable gas, lowmass bcg and taccom lowmass buffers and reduced power buffer springs.

[PNWTargets]

I use Superlative Arms adjustable gas blocks. An adjustable gas block is the only way to correctly adjust gas flow and adjust the BCG with buffer and spring combo. The lighter the BCG and spring set up is the less gas needed to move them. But BCG total travel (short stroke/speed of BCG stroke, and last round bolt hold) are factors. Different spring weights and buffer weights are something you need to set up if you want to set things up correctly. I would dump the rifle length buffer set up and get carbine set up due to more options and less overall weight.

[A5BLASTER]

I use Superlative Arms adjustable gas blocks. An adjustable gas block is the only way to correctly adjust gas flow and adjust the BCG with buffer and spring combo. The lighter the BCG and spring set up is the less gas needed to move them. But BCG total travel (short stroke/speed of BCG stroke, and last round bolt hold) are factors. Different spring weights and buffer weights are something you need to set up if you want to set things up correctly. I would dump the rifle length buffer set up and get carbine set up due to more options and less overall weight.

You can get rifle buffers that weight the same as carbine buffers. No reason to go from a smoother buffer action to a harsher working one.

[tdbru]

i guess if i want to go to an adjustable gas block, the first order of business will be to see what the barrel OD is for the current gas block and see if anyone makes an adj gas block with the diameter that would fit the barrel i have.
thanks,
-tdbru

[A5BLASTER]

i guess if i want to go to an adjustable gas block, the first order of business will be to see what the barrel OD is for the current gas block and see if anyone makes an adj gas block with the diameter that would fit the barrel i have.
thanks,
-tdbru

Who made the barrel? They can tell you exactly what size gas block it uses.

[PNWTargets]

A5Blaster ok.