Theoretically piston works better than DI for short barrels because gas has to travel all the way back through gas tube to the bcg in a DI system before bullet leaves barrel, whereas gas only has to go from gas port to piston head in a piston system.
Is this correct?
Almost all battle rifles and assault rifles out there not based on AR10/AR15 are piston operated, and really for all technical intents and purposes, DI is still a piston operation, just not quite a closed piston.
if works better = marginally higher cyclic rate, then sure
you're not one of those 'ar15 is piston but the piston is behind the bolt/ar15 is not DI' tards, are you?
>DI is still a piston operation
No it isn't. An AR-15 is not DI, it uses an inline piston with an expansion chamber. This means there is no carrier tilt and the recoil is more mild while also only being directly backward. It is a super clever design, which is why it is so widely used.
You just blow in from stupid town or something?
Within context, I was referring to AR-15 DI systems, which isn't really DI but in fact a form of piston.
Yes this is correct. DI is better for inline recoil and piston is better for reliability with a short barrel imo.
But it literally is, you fucking mong. There is nothing in the system that is being directly impinged. There is an expansions chamber behind and beneath the gas key that is completely counter to what a direct impingement system would be.
This fucking gif again...
I don't think it's because the gas has to travel further back. I think AR-15s struggle with shorter barrels, especially while suppressed, not necessarily because it's "DI" but because it's still the design from rifle length gas system and 20" barrel (mainly regarding the cam path, extractor, and gas rings) that's forced to operate as a short barreled gun with very few changes.
More modern guns like the SCAR, which was designed around suppressed short barrels, have cam paths that unlock the bolt much later and more gradually which let chamber pressures significantly drop and makes extraction much easier. AR cam path is a lot more immediate which works fine with the lower port and chamber pressures of the rifle length gas system but with super short barrels it requires a lot more force to extract.
The original gas rings, which look like they're made of coke cans, and extractor were also probably designed with the port pressures and dwell time of the rifle length gas system in mind as well. Once you go to the carbine length gas system (much higher port pressures), chop the barrel super short that cuts the dwell time (so they have to bore the port big to get it to cycle), then put a can on the end with no sort of way to regulate the gas down, it just beats up the system and it just gets worse as the gas port erodes. As a result long term durability suffers, though upgrades like better extractors/extractor springs, mcfarland gas rings, stronger bolts, better gas regulation, more dwell time (like 11.5" barrels compared to 10.3") go a long, long way to make it better.
I believe the "DI" system can easily work great with shorter barrels but it would require a complete redesign with that in mind, losing its compatibility many standard AR-15 parts which sort of defeats the purpose.
Gas is directly impinging on the gas key, which is part of the bolt carrier group. Gas is a physical object in scientific terms. It may not be a solid, but it has a molecular structure, and a mass that can be measured, like air. Therefore, the gas escaping into the gas tube IS directly touching/impinging on the bolt, fucktard. The term is not direct impingement, but direct GAS impingement.
piston guns are just direct gas impingement then, the gas directly impinges on the piston.
I mean that'd be the round's fault – part of the reason why the AKM is so rugged is because it's designed around the round having excessive gas that it then ignores past what is needed to cycle, so if the round has a bit less propellant due to manufacturing fuck ups, and if the barrel is shortened and the gas pipe moved nearer the chamber the decrease in gas volume hitting the piston means that it vents less rather than it struggling to cycle.
But the ARs are designed to be *efficient*, so shorten the barrel and fuck up the propellant amount? It ain't gonna cycle, you start getting squibs etc...
The shift to "intermediate" rounds further exacerbated the problem, by the time people were chambering it in .22 the DI system on them is so hungry for gas I'm surprised they don't just fit an air canister from an air rifle onto it and leave gunpowder out of the mix entirely.
Except that the "impingement" portion of the designation refers impingement on the the bolt group, nothing else.
There is a little bit of "marketing buzzword" about DI, there's still a spring and still sort of a pistony thing, but it's part of the bolt, but it's not a "bolt piston" it's a "direct impingement" and "has no piston" and thus "saves in number of parts" despite it really being two parts fused together like something from a version of annihilation that's about guns getting fused together rather than animals.
then every long stroke piston system is direct impingement. Take the BCG of the ak platform as example, The piston on the AK bolt carrier is basically the exact same thing as the gas key on the AR bolt carrier.
By your definition only short stroke piston systems aren't direct impingement.
All of what you're saying is technically correct, but direct gas impingement like on a MAS-36 is gas coming back to a cup or a plate and said gas driving the bolt back. That is not the case in an AR. The gas comes through the gas key, enters the expansion chamber, and the bolt carrier and bolt piston as they move back during the operation of the rifle. The fact that it's not a short stroke gas piston gun doesn't change the fact that it's still a piston gun. The piston just happens to be located in-line with the action of the gun and formed by the bolt and the bolt carrier group.
>Stoner put a gas key and piston rings on the AR bolt for shits and giggles
You eat too many paint chips as a child or something?
The compression wave will travel at the speed of sound in air at that state, which although is much lower than the speed of sound in steel or what have you, the difference on a human scale is minuscule.
From Eugene Stoners own patent "This invention is a true expanding gas system instead of the conventional impinging gas system. "
patents.google.com/patent/US2951424A/en
Bolt, or bolt carrier group?
The AR isn't DI
Also less hot gasses in the receiver/trigger/magazine so it runs cleaner for longer.
No, the speed of sound in hot, compressed propellant gas is like 5000fps, so it's only a fraction of a millisecond difference. And if you still think that's a problem, just move the gas port back a little to compensate for it.
>used
By like, three countries.
The original AR-15 has a gas piston behind the bolt.
>forces hot gas and carbon fouling into the receiver and chamber
wtf, did the person who made this ever shoot or even look at a Ar-15 in person?
It's used by the entire world, America.
AR-15s are as much DI as a weapon can be.
patently false.
the Ljungman Ag m/42 is much more DI than the AR-15
shits where it eats
>Is this correct?
no, because you want a *longer* dwell time not a shorter one. the case needs time to contract.
Short-stroke piston
Pros:
-Slightly less heat/carbon into the bcg
-No gas tube to get water into/no need to drain water from your for 2 seconds after coming out from a scuba dive
Cons:
-More parts wear from more violent action
-Recoil increased due to the piston going back and forth
-Heavier gun due to piston
So unless you need a gun that you can fire immediately as you exit a fucking lake or if you're trying to fire thousands of rounds on full auto without cleaning your gun there are 0 pros to having a short stroke piston.
Are legit retarded? Nearly every single special ops team on Earth uses an AR pattern rifle. What are you fucking smoking retard?
It's a stationary piston, deal w/ it
And? DI AR's malfunctioning from a lack of cleaning isn't even a thing unless you literally shovel mud into open chamber
>What is literally everywhere except for Eastern Europe and most of Africa
Both Russia and China manufacture and sell them to african countries. Pretty much the whole world should be colored in.
>2008
why come nobody has designed a gun that shoots the carbon forward with the bullet? that way it's always clean
yeah, because that's one more thing he can charge for under the patent. this your first rodeo with product designers?
That's called recoil operation