Hey /k/, got a question for you.
In a gas piston system with a rotating bolt, how does the bolt unlock from the chamber? I know in a DI AR, the gases go inside the bolt and push it slightly forward to relieve a little of the backwards pressure on the bolt so it can unlock, but it appears that in a piston gun (whether or not it's an AR) the piston only provides a backwards push on the BCG, which I would think wouldn't work because it doesn't have that little forward push to release it from the locking lugs. Anyone here that can explain this?
Wondering because I'm working on my own design (idk if I'll ever have the motivation/time/resources to try and make it but I am having fun with designing it alone). I am also wondering if the part of the bolt with the extractor claw can strip a round from a magazine or it something special would have to be done to make that work?
If anyone else has any questions post them here and maybe we can all learn something today.
Pic related.
I don't have an answer to the OP but I do have a question regarding DI versus gas piston: are gas piston guns inherently less accurate or does that only apply to ARs?
Bumping, I'm sure someone here knows the answer.
>>29276328
Depends on design i guess. With di there is a much longer dwell time before the piston in the bcg fires and cycles the action, giving the bullet time ti exit the muzzle before anything happens, not sure how true that is for piston designs.
I beleive the scar and mdr(vaporware till actually released) have sub moa? Accuracy from ss gas piston designs.
>>29276211
>push it slightly forward to relieve a little of the backwards pressure on the bolt so it can unlock
Stop perpetuating this myth
Where is my dad?
>>29276567
Is that not true? Then why do the gasses go into the bcg in the first place?
>>29276604
to push the bolt carrier back in a perfectly straight line
It was NEVER intended to relieve bolt lug pressure
Not one other gun in existence does this
>unless they use the same Stoner fluid piston system
>>29276611
Is that why DI is more accurate?
>>29276328
In a piston system there's a lot of mass moving just on top of the barrel and chamber, depends on the design and construction anyways...
>>29276639
Straight line recoil has nothing to do with accuracy
The reason the AR is accurate is due to full and square bolt lockup, a completely free floated barrel, and a completely round, completely flush barrel mounting design (barrel nut)
And the AR in itself is not inherently accurate
That has more to do with companies constantly competing for business and making their product better than competitors
Milspec is 4 MOA for ARs
Now, ARs DO have a low recoil because of the perfectly inline design, but recoil is not accuracy
>>29276659
can you explain to me why the rdb range reports have seemed to unanimously say it has low recoil despite not using that gas system?
>>29276720
>can you explain to me why the rdb range reports have seemed to unanimously say it has low recoil despite not using that gas system?
Wait what?
The AR uses the Stoner Fluid Piston system which is erroneously titled DI
>>29276739
for all intents and purposes the stoner AR15 design is a DI system
>>29276750
true DI just smashes gas into the face of the bolt
ARs do not
It vents out the holes in the side of the bolt
A true Ljungman Di system is only slightly better than piston and that's because it simply removes reciprocating weight, but it still raises the pivot point
There is no pivoting in the Stoner fluid piston system
>>29276720
wait, are you referring to the Keltec RDB?
if you are, the recoil is low because it's a bullpup
In a bullpup you are holding MUCH further up to the end of the barrel, therefore you have much more leverage to hold it down
And the bore axis to your shoulder is lower than the traditional AR as well
>>29276768
no one gives a fuck sperg
>>29276604
This is not entirely true. While the gasses do provide a forward force to the bolt, reducing frictional wear, it is not the sole action that causes the bolt to unlock. Also fyi the DI variant of the OP gif is incorrect. Hot gasses aren't just vented into the receiver.
In DI, gases push against a gas key on the bolt carrier, which functions effectively like a piston, just located in the receiver and fixed to the BCG, more or less.
A shot is fired and the gasses provide impulse, causing the BCG to move rearward, the bolt stays locked to the chamber. Its movement is blocked by radial lugs that line up on the bolt and in the chamber. The BCG has a vaguely S shaped cutout in which a cam pin (Green in gif) is seated. The cam pin is fixed to the bolt. This acts as a cam surface which rotates the bolt a few degrees, moving the lugs out of alignment and enabling the bolt to travel rearwards freely. Momentum takes over the rest, spring potential energy returns the bolt and the same camming action happens in reverse.
http://www.cruffler.com/AR180BoltGroup1.jpg
This is a stripped AR-18 bolt group. You can see the cam cutout and the cam pin. The cam pin is attached to the bolt
>>29276768
In the same way internal combustion engines are defined by them all all using carburetors? All this nonsense EFI shit isn't true combustion.
New technologies and new methodologies will always surpass old ones. AR-15 is as DI as an M42 ljungman is DI.
>>29276768
So in that case you're basically deciding if you want a slightly higher reliability or a slightly nicer recoil when choosing systems?
>>29276772
>I have a question and need detailed information guise
>alright here's a detailed answer on how things work and how they differ from other things
>JESUS NO ONE CARES MAN
>>29276784
>New technologies and new methodologies will always surpass old ones. AR-15 is as DI as an M42 ljungman is DI.
No it's fucking not and it never has been
DI is the erroneous term people gave to it
The AR action designed by Eugene Stoner is commonly called a direct impingement system, but it does not utilize a conventional direct impingement system. In U.S. Patent 2,951,424, Stoner states that the system is not a conventional impinging gas system: ″This invention is a true expanding gas system instead of the conventional impinging gas system.″[2] Gas is routed from a port in the barrel directly to a chamber formed in the bolt carrier.
>>29276784
>In DI, gases push against a gas key on the bolt carrier, which functions effectively like a piston, just located in the receiver and fixed to the BCG, more or less.
>A shot is fired and the gasses provide impulse, causing the BCG to move rearward, the bolt stays locked to the chamber. Its movement is blocked by radial lugs that line up on the bolt and in the chamber. The BCG has a vaguely S shaped cutout in which a cam pin (Green in gif) is seated. The cam pin is fixed to the bolt. This acts as a cam surface which rotates the bolt a few degrees, moving the lugs out of alignment and enabling the bolt to travel rearwards freely. Momentum takes over the rest, spring potential energy returns the bolt and the same camming action happens in reverse.
You have completely ignored the internal expansion chamber that the gas key funnels gas into
It goes into that chamber, expands, then vents the gas out the bolt ports after unlocking
>>29276785
the AR system is not inherently unreliable
while it *technically* can foul up catastrophically, people have run basic ARs with modern ammunition for 10s of thousands of rounds without cleaning to no ill effect
In fact, the Ljungmans get incredibly fucking dirty due to their design
And so do you because it vents over the top
Guy in the Swedish army when it was issue told me that you always got some smoke in your eyes when firing quickly
>>29276801
Yes but it does directly impinge on a bolt carrier, does it not?
>>29276806
Fuck that, not really important. The gas is vented away after the initial impulse almost exactly like a piston system. The expansion chamber is a fairly minor detail in the whole system and is not relevant as to how the bolt unlocks.
>>29276822
>Yes but it does directly impinge on a bolt carrier, does it not?
By that logic gas directly impinges on the bolt carrier of an AK because the piston is affixed to it
Stoner even said that it's not conventional
YES it does push on the bolt carrier, however, it is not the definition of DI
And if you want to go start changing definitions, you can go back to Tumblr, you SJW
>Fuck that, not really important
That is literally THE most important part
It expands INSIDE the bolt carrier and pushes it back instead of simply smashing into it and then venting out the side
This makes it recoil in a perfectly straight line UNLIKE DI, piston, or other systems and then vents it out the side keeping the rifle clean
That is ABSOLUTELY the #1 most important design to the AR-15 operating system
>>29276838
"Direct impingement is a type of gas operation for a firearm that directs gas from a fired cartridge directly into the bolt carrier or slide assembly to cycle the action."
The AK's gas system doesn't directly impinge on the bolt carrier you fucklord, it impinges on an external piston.
Gas expanding inside the BCG does nothing (or at least, very little) as far as rearward impulse is concerned. This is how physics work. Filling any chamber with pressure won't impart a force on it (which includes changing the magnitude and direction of existing forces, such as those imparted on the gas key). It does regulate the timing of the venting, among some other things, sure, but it's in no way the '#1' most important thing about ar-15 gas systems.
>>29276838
>Direct impingement is a type of gas operation for a firearm that directs gas from a fired cartridge directly into the bolt carrier or slide assembly to cycle the action.
> directly into the bolt carrier or slide assembly to cycle the action.
>directly into the bolt carrier
>>29276880
>The AK's gas system doesn't directly impinge on the bolt carrier you fucklord, it impinges on an external piston.
which is directly attached to the bolt carrier
>Gas expanding inside the BCG does nothing (or at least, very little) as far as rearward impulse is concerned.
Then you don't understand how it works
>Filling any chamber with pressure won't impart a force on it
When the gas expands, it will push the bolt carrier backwards because the bolt carrier is moveable
pressure flows from high to low and will try to expand whenever possible
being as the bolt carrier is the point of least resistance, it will push that backwards
It expands quickly enough that the bolt carrier will retain it's momentum and cycle the firearm
that's why if you put a 16 inch barrel on a rifle length gas, it doesn't cycle for shit because there isn't enough gas in that expansion chamber to put enough momentum onto the carrier
>>29276816
I'm not saying it's unreliable, just that a piston system will generally be a bit more reliable. Also, you run a little cooler, etc...
>>29276792
Hey, as the person who you've been answering for, I appreciate the detail.
>>29276922
>piston
>more reliable
>cooler
this is all wrong
>>29276906
Holy fuck I'm gonna break this down for you buddy because you're not understanding this and I honestly thought a 5 year old would be able to spot the difference.
A piston ATTACHED TO a bolt carrier =/= a bolt carrier
If you can't understand this I'll probably just fucking blow my brains out now.
>>29276922
Yes in theory it would be, except many piston designs can and do bend the shafts
I've seen SKSs and FALs do this
That said, piston ARs are not because of carrier tilt
ARs are simply not designed for piston use due to no bolt rails
>>29276936
>pistons and shit no cool as fuck
I think you're wrong m8
>>29276944
buddy I've been trolling you on the piston thing
I was simply parodying the idea that any force imparted on a part attached to a bolt carrier qualified as DI
I am fully aware that long stroke piston requires pistons attached to the carrier
>inb4 damage control
I'm not stupid m8, I know how guns work
>>29276951
pistons are for poorfags that can't do proper engineering
>>29276961
it's ok man
They're fucking magic sorcery I think
>>29276963
Cars are for poorfags then
>>29276947
So if you give your bolt/bcg rails to ride one it will prevent tilt?
>>29276974
>he doesn't have a tesla
>>29276997
yes
hence why dedicating piston designs all have bolt rails
>>29277015
Ok, in that case I'm gonna need a list of guns (preferably more modern) to research their piston rail systems.
>>29277032
they're just woodruff cut slots on the carrier or receiver m8
>>29276211
This is a misunderstanding. If you read the original patents the point is that the bolt acts as a stationary piston while the bolt carrier is the moving cylinder. The gas enters the expansion chamber and forces the bolt carrier back because the bolt is pressed against the barrel extension.
Y'all know what's cool?
Ice cream. Ben n Jerry
I don't get how semi-auto pistols work. Are they gas operated?
>>29278473
blowback
>>29278528
Would you hapoen to have a .gif?
>>29278528
More precisely, short recoil for most locked breech designs, straight blowback only for lower powered unlocked designs.
>>29276211
>In a gas piston system with a rotating bolt, how does the bolt unlock from the chamber?
It's cammed back by the op rod forcing the guiding pin on the bolt.
