Piston in the buffer tube?

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superlative

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I don't know that much about rifle engineering, but a thought occurred to me: why not have a piston based AR, where the piston is in the buffer tube? The gas tube would snake all the way back to the buffer tube area and apply to a piston in the buffer tube?

All piston based rifles are inherently inaccurate because the piston sits above the barrel, causing interference with the barrel harmonics. Gas impingement rifles are accurate because the gas is applied directly to the bolt carrier group, thereby resulting in no interference with barrel harmonics; the problem is that dirty gas is spewed into the bolt area.

Presumably if the gas tube went all the way to the buffer tube area, and a piston could be applied there, then it would solve two problems:
1. No barrel harmonic interference
2. no dirty gases in the BCG

I suspect that there are other problems that I'm not considering?
 
I'm going to have to go with "if it ain't broke, don't fix it". My gas guns get nice and dirty but it's never been to the point where it causes issues.
 
Excess gas needs to vent somewhere....in the M14 it's out the bottom of the gas cylinder, in the AR15 it's out the ejection port.
If you ran it back to the buffer tube, it's gonna vent into your face lol.
 
Wont work, gas cools by the time gets there and when hot gas cools all sorts of gunk starts condensing on everything it touches
The proper way to make a piston gun accurate is to have a free float handguard with the gas piston attached to the handguard.
The gas block would then have a skimpy not very rigid short tube going to the piston (or it could be a sliding arrangement)

For all practical purposes you have a free floated piston gun with all the positives of DI and piston without any of the negatives

You would think with the millions of tax dollars goverments across the world spend to try and figure it out, that they would make some forward progress once in a while...
 
"Dwell time" would probably be an issue.

I imagine it'd get clunky back there as well (lose cheek weld.)
Lastly, if something were to fail, higher chance of hot gas and metal in the face :)

Good to think outside the box though.
 
Piston guns are not inaccurate, think of the HK SL8, Bushmaster ACR, and my PWS AR. I've shot sub moa groups through all of those rifles. It's more about barrel quality and ammo selection, the HK uses a Lothar Walther, my ACR has a match grade stainless, and the PWS has a stainless high end barrel. The PWS I own isn't even free floated and it can shoot moa with Black Hills mk262 77gr.
I think too much emphasis is placed on accuracy in the rifle these days, most rifles are capable of shooting a lot better than most think they can if the owner were to work on their shooting skills and also finding what ammo a barrel likes through experimentation and/or load development. You can't expect a rifle to shoot tiny groups if you feed it 55gr surplus. My PWS shoots 55gr AE into around two to two and a half inches at 100yds even though it can shoot sub moa with premium ammo.

Also, as 2stroke mentioned there are ways to improve the piston system, I believe Adams Arms has a system like what he described which performs well.
 
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superlative said:
I don't know that much about rifle engineering, but a thought occurred to me: why not have a piston based AR, where the piston is in the buffer tube? The gas tube would snake all the way back to the buffer tube area and apply to a piston in the buffer tube?

All piston based rifles are inherently inaccurate because the piston sits above the barrel, causing interference with the barrel harmonics. Gas impingement rifles are accurate because the gas is applied directly to the bolt carrier group, thereby resulting in no interference with barrel harmonics; the problem is that dirty gas is spewed into the bolt area.

Presumably if the gas tube went all the way to the buffer tube area, and a piston could be applied there, then it would solve two problems:
1. No barrel harmonic interference
2. no dirty gases in the BCG

I suspect that there are other problems that I'm not considering?
Click to expand...

You aren't considering how an AR actually operates. How do you expect applying gas pressure behind the bolt is going to make it unlock and move backwards? There is no firearm on earth that operates this way and for good reason. Its like trying to make a car go by applying the brakes.
 
Maybe you could put the piston inside the bolt carrier group and make a tube for the gas to get there that free floats throuh a hole in the upper reciever so the "gas tube" doesn't affect barrel harmonics.

That would leave room in the butt for an action spring and maybe a weight to buffer out bolt bounce on automatic.

Since the piston would be in line with bore and the moving parts would recoil in line it woukd be inherently accurate and reliable.

You could probably sell millions and get over fifty countries to adopt it as their military rifle.
 
cr5 said:
Piston guns are not inaccurate, think of the HK SL8, Bushmaster ACR, and my PWS AR. I've shot sub moa groups through all of those rifles. It's more about barrel quality and ammo selection, the HK uses a Lothar Walther, my ACR has a match grade stainless, and the PWS has a stainless high end barrel. The PWS I own isn't even free floated and it can shoot moa with Black Hills mk262 77gr.
I think too much emphasis is placed on accuracy in the rifle these days, most rifles are capable of shooting a lot better than most think they can if the owner were to work on their shooting skills and also finding what ammo a barrel likes through experimentation and/or load development. You can't expect a rifle to shoot tiny groups if you feed it 55gr surplus. My PWS shoots 55gr AE into around two to two and a half inches at 100yds even though it can shoot sub moa with premium ammo.

Also, as 2stroke mentioned there are ways to improve the piston system, I believe Adams Arms has a system like what he described which performs well.
Click to expand...

Wow - here is a video of it:

Basically they adapted the CZ-858 piston system to the AR-15. Brilliant!
 
Matt K said:
Maybe you could put the piston inside the bolt carrier group and make a tube for the gas to get there that free floats throuh a hole in the upper reciever so the "gas tube" doesn't affect barrel harmonics.

That would leave room in the butt for an action spring and maybe a weight to buffer out bolt bounce on automatic.

Since the piston would be in line with bore and the moving parts would recoil in line it woukd be inherently accurate and reliable.

You could probably sell millions and get over fifty countries to adopt it as their military rifle.
Click to expand...

Ummm, piston in the BCG? You mean like a direct impingement rifle?
I can't tell if I'm misunderstanding you or if you're joking to make a point that the DI rifle already does this.
 
Here's a better idea: blow forward action!

Here's an actual rifle with this action, the Sig AK53:
ak53b.jpg


One would think this system would have 2 advantages:
1. Cleaner
2. Lighter - no extra parts
 
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That video of the adam arms is not what I am talking about, what I want is a gun where the torque of the gas piston pushes in between the handguard and bolt carrier

That adam arms system pushes off the barrel
 
Nope, I want the piston housing attached to a free floating handguard...and a nice flexible connection from the gas port to piston housing

The barrel is effectively free floating like an ar but:
No mess in the carrier
Suppressor friendly
Easier to clean/ more reliable
 
Same thing as the relativly flexible gas tube on a ar... Lol

Obviously not going to use slingshot tube, and it wont truly be free floating, anymore than an ar with gas tube attached
 
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