It really depends entirely on one's definition of a piston. In most machines with a piston, the piston is there to impart force on another component. In an AR, the bolt is the end component so calling it a piston is questionable. With a loose enough definition we could call a cartridge a piston. Really, it's all an argument of semantics and therefor contributes nothing to the discussion.
Not all pistons move. Sometimes the cylinder moves. Sometimes the cylinder
and the piston moves. Take a look at various hydraulic systems. It's not semantics, it's language and clearing up misunderstanding always contributes to the conversation- and yes, the bullet is a piston without a connector rod
Except with a DI gun there is very little "venting". The carbon gas enters the receiver where it cools and solidifies. Regarding a piston system, who cares if its under the handguards? It can't impart resistance to operation of any components there. And since the cavity gas enters from the barrel is much smaller in a piston gun far less enters the action as well. Once the piston finishes its rearward travel the pressure in front of it rapidly rises so less gas enters from the barrel.
The legacy system has plenty of venting. The gases vent from the two vent holes in the carrier. It vents from the gas tube. It vents fromthe muzzle. The carbon only solidifies if the rifle is run without proper lubing. With proper lubing, it's a gooey mess
. I find this to be true of all firearms. Why do we care about crapola under the handguards? Because we have pistons and op-rods under there
I'm not knocking DI AR's. With standard civilian barrel lengths and the limitation of semi-auto fire a properly built DI gun will meet the needs of the vast majority of civilians. Any advantage a well made piston system offers in such scenarios will rarely, if ever be observed. Now if we chop the barrel, slap on a silencer and run full auto, well, that's another story.
I know LAV has stated the PIGB has an advantage with SBRs, suppressors and running full auto. But I think the advantage is overstated. More work has been done to tune SBRs to run properly with and without a suppressor and that advantage is gone
Kind of sounds like you're looking for a fight on this one Mist. I'm froggy.
I made that statement with two purposes in mind- To see if anyone is really reading the posts in this thread or just glancing through. The other is to clarify what were talking about
It's just great that you pulled the Stoner patent and all and figured out the bolt of the AR is actually a piston AND bolt. Pretty much common knowledge at this point and all of the people who own piston rifles have recommended DI....Yet you still continue.
Folks keep talking about adding a piston to the AR. What reinforces this is the misconception the AR uses a DI system. The conversation becomes "why are we adding a piston?" when in reality it should be "why are we moving the piston from the carrier to the gas block?" or even "why did Stoner move the piston from the gas block to the carrier and eliminate the op-rod?" Without asking the right questions, we cannot find the right answers
-After how many rounds and at what sustained fire rate? Answer: No matter how many rounds, hotter than a piston rifle. Ever melt a gas tube?
But how much hotter? Does the bolt and carrier get hot enough to matter? Even if the tube melts, does that mean the BCG is also that hot? Why does the tube melt?
Where does the tube melt? How hot is the gas block when the tube melts? How hot is the barrel and where is it the hottest? If a piston were in the gas block under the same conditions, how hot would it be? What state would the piston material be? Solid? Plastic?
While I've never heated up carbine enough to melt a gas tube, I've gotten the barrel and gas block hot enough to boil water. When I pulled the BCG out, the bolt was a bit hot as was the gas key but the carrier itself was barely warm. Most of the heat from the gas gets dumped at the gas block. Simple thermodynamics
It's a simple matter of where you want your heat and dirt. Do you want it in your receiver and on your bolt where it can and will eventually interfere with feeding and reliability or worse crack your bolt from the stress of hot / cool cycles? Or do you want it outside the barrel and in the hand guards where the odds of it cracking your bolt or requiring copious amounts of oil are remote.
There, you and I have now sent this into the Piston / DI death spiral.
The bolt gets most of it's heat from the chamber and from the case. The gas dumps much of it's heat at the gas block after it passes through the gas port. The gas block has a small chamber where the pressure drops and the gas dumps it's heat. It's how your refrigerator works. The gas carried to the carrier has cooled quite a bit, dropped in pressure and slowed in velocity. It's also has little mass. The powder charge is only a few grains to start with and most of that gets blown out the muzzle
