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Author Topic: Short stroke Vs long stroke  (Read 2282 times)
Tvfreakarms
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« on: July 28, 2018, 04:29:22 PM »

What was the point of changing the tavor from long to short stroke gas piston on their tavor 7?

The big thing for me is, I'm also wondering where the excess gasses get expelled out of?

Is it out and front of the muzzle area or is it still shots the gasses back into the inside rec? What the sar/x95 and even the MDR from what I read.

Especially shooting it suppressed. Im sure we all seen the videos of how pretty nasty it gets inside the tavor.
Makes a Di AR rifle  clean 😂.

LLAP

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DOWNS
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« Reply #1 on: July 28, 2018, 09:22:08 PM »

I'd imagine that if they need less gas they will make the gas port smaller or if it has an adjustable gas valve make the ports on that smaller.
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HBeretta
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« Reply #2 on: July 29, 2018, 03:37:50 AM »

What was the point of changing the tavor from long to short stroke gas piston on their tavor 7?

Less gas and less recoil which makes sense in 308 with higher cyclic rate in full auto.  Consensus is long stroke is more reliable...it seems, but we’re talking the Toyota of firearms here in IWI.
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Tvfreakarms
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« Reply #3 on: July 29, 2018, 05:29:41 AM »

Does anyone know where the excess gasses escapes?
Is it inside the rec or shots out toward the muzzle?
From what I read, and seen slow motion, it seems it still escapes inside the rec. Which I don't get.

LLAP

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HBeretta
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« Reply #4 on: July 29, 2018, 07:51:20 AM »

Does anyone know where the excess gasses escapes?
Is it inside the rec or shots out toward the muzzle?
From what I read, and seen slow motion, it seems it still escapes inside the rec. Which I don't get.

LLAP



you have gas escaping from the gas cylinder which unfortunately is located further back(closer to shooters face) on an x95/tavor - see below vid that was thrown up recently with regard to this.  the gas cylinder on an rdb for example is located further up on the rifle closer to the muzzle, and especially on an fs2000.  the major advantage with the rdb with regard to excess gas is how you can fine tune the gas to the ammo being used along with the receiver design minimizing excess/residual gas in the shooters face as it escapes through the downward ejection chute - especially when suppressed.  you mentioned suppressed and assumed gas blowback due to the baffles sending gas backwards.  oss threw up a vid few years back along with MAC recently speaking to eliminating this in his MDR vid - see below.  now i'm curious as to the internal design of the t7, but it appears the gas cylinder is further up or closer to the muzzle in looking at photos...the gas adjustment knob being the giveaway.  from there i guess it's rifle design as to how residual gasses flow out of the receiver; alibrando speaks to this in the tavor vid below...some users complaining it seeping through the butt-pad on the MDR and so on.  anyway, not sure if this helps.

x95 gas reduction
https://www.youtube.com/watch?v=5FDOXK2p0N0

gas blowback
https://www.youtube.com/watch?v=c0uYVFj_M8Y

rdb suppressed efficiency (gas venting downward)
https://youtu.be/ESGwQS-JW40?t=7m46s

« Last Edit: July 29, 2018, 01:00:06 PM by HBeretta » Logged
Tvfreakarms
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« Reply #5 on: July 29, 2018, 08:02:18 AM »

Interesting.
I know there was a lot of complaints about the sar/x95 having the gas face from the gas port. I was really surprised how much of it when it was suppressed.
Hopefully iwi fixed this issue. By having the gas going out or it's toward the muzzle.
I believe Adams arm's piston rifles shoots gas out the front toward the muzzle.
Does anyone know where the excess gasses escapes?
Is it inside the rec or shots out toward the muzzle?
From what I read, and seen slow motion, it seems it still escapes inside the rec. Which I don't get.

LLAP



you have gas escaping from the gas cylinder which unfortunately is located further back(closer to shooters face) on an x95/tavor - see below vid that was thrown up recently with regard to this.  the gas cylinder on an rdb for example is located further up on the rifle closer to the muzzle, and especially on an fs2000.  the major advantage with the rdb with regard to excess gas is how you can fine tune the gas to the ammo being used along with the receiver design minimizing excess/residual gas in the shooters face as it escapes through the downward ejection chute - especially when suppressed.  you mentioned suppressed and assumed gas blowback due the the baffles sending gas backwards.  oss threw up a vid few years back along with MAC recently speaking to eliminating this in his MDR vid - see below.  now i'm curious as to the internal design of the t7, but it appears the gas cylinder is further up or closer to the muzzle in looking at photos...the gas adjustment knob being the giveaway.  from there i guess it's rifle design as to how residual gasses flow out of the receiver; alibrando speaks to this in the tavor vid below...some users complaining it seeping through the butt-pad on the MDR and so on.  anyway, not sure if this helps.

x95 gas reduction
https://www.youtube.com/watch?v=5FDOXK2p0N0

gas blowback
https://www.youtube.com/watch?v=c0uYVFj_M8Y

rdb suppressed efficiency (gas venting downward)
https://youtu.be/ESGwQS-JW40?t=7m46s

LLAP

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BullpupT
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« Reply #6 on: July 31, 2018, 08:01:14 AM »

Recoil is reduced with short stroke systems due to the use of lighter bolt assemblies. They have less reciprocating mass which helps with faster follow up shots.

Think of it like an AK/PSL vs. SVD. The both look very similar yet they are completely different. You get much faster follow up shots with a lighter short stroke bolt.
« Last Edit: July 31, 2018, 08:28:56 AM by BullpupT » Logged
blottogg
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« Reply #7 on: July 31, 2018, 11:23:36 PM »

With the two-stage, long stroke piston on the original Tavor, the cylinder extends almost to the breach of the barrel, and the piston actually clears the cylinder at the end of the bolt carrier's travel, dumping any residual gas into the guts of the receiver.  Unsuppressed, the piston/recoil spring, etc. are designed so that there's little gas pressure remaining at the full length of travel, so not much gets dumped into the shooter's face.  Suppressed, there's more gas fed to the cylinder, and that excess gas dumps into the receiver like a DI AR.  From what I've seen of the Tavor 7, the short-stroke piston doesn't extend nearly as far towards the breech as the long stroke setup (as you'd guess from the names), the gas being confined to a smaller cylinder in what you can think of as a big gas block towards the barrel (there's a push rod transferring the motion to the bolt carrier, without any plumbing for gas).  the valve adjustment knob for the gas cylinder is on the front of this block, so I'm assuming that the vent for any excess gasses is on the front of the block also, and should vent forward.  That there's a setting for suppressors on the adjustment knob also means that less gas is being tapped from the barrel on that setting, which should prevent any over-gassing to begin with.

The main differences between short and long stroke gas piston setups are that long-stroke is mechanically simpler (the piston is part of the bolt carrier group) and self-regulating (over-gassing just gets vented at the end of the piston's stroke, though as noted, that can leave a mess), while the short-stroke setup is more expensive (more parts to make) and cleaner, with the gasses confined to a smaller cylinder at the front of the weapon, and can be made adjustable with a valve at the gas port.  I guess you could make long-stroke systems adjustable with a valve as well, but I haven't seen a setup like that.
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Tvfreakarms
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« Reply #8 on: August 01, 2018, 12:07:25 AM »

Interesting. I was just curious of where the excess gasses are going to be dumped.

My thinking was why make a piston rifle that will dump excess gasses back into the rifle this creating more gasses potentially in the face and make the rifle really dirty. Especially when it's suppressed.
I know there is a youtuber who showed what it looked like afterwards. I don't think I've seen a dirtier rifle.
With the two-stage, long stroke piston on the original Tavor, the cylinder extends almost to the breach of the barrel, and the piston actually clears the cylinder at the end of the bolt carrier's travel, dumping any residual gas into the guts of the receiver.  Unsuppressed, the piston/recoil spring, etc. are designed so that there's little gas pressure remaining at the full length of travel, so not much gets dumped into the shooter's face.  Suppressed, there's more gas fed to the cylinder, and that excess gas dumps into the receiver like a DI AR.  From what I've seen of the Tavor 7, the short-stroke piston doesn't extend nearly as far towards the breech as the long stroke setup (as you'd guess from the names), the gas being confined to a smaller cylinder in what you can think of as a big gas block towards the barrel (there's a push rod transferring the motion to the bolt carrier, without any plumbing for gas).  the valve adjustment knob for the gas cylinder is on the front of this block, so I'm assuming that the vent for any excess gasses is on the front of the block also, and should vent forward.  That there's a setting for suppressors on the adjustment knob also means that less gas is being tapped from the barrel on that setting, which should prevent any over-gassing to begin with.

The main differences between short and long stroke gas piston setups are that long-stroke is mechanically simpler (the piston is part of the bolt carrier group) and self-regulating (over-gassing just gets vented at the end of the piston's stroke, though as noted, that can leave a mess), while the short-stroke setup is more expensive (more parts to make) and cleaner, with the gasses confined to a smaller cylinder at the front of the weapon, and can be made adjustable with a valve at the gas port.  I guess you could make long-stroke systems adjustable with a valve as well, but I haven't seen a setup like that.

LLAP

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BullpupT
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« Reply #9 on: August 01, 2018, 08:00:03 AM »

With the two-stage, long stroke piston on the original Tavor, the cylinder extends almost to the breach of the barrel, and the piston actually clears the cylinder at the end of the bolt carrier's travel, dumping any residual gas into the guts of the receiver.  Unsuppressed, the piston/recoil spring, etc. are designed so that there's little gas pressure remaining at the full length of travel, so not much gets dumped into the shooter's face.  Suppressed, there's more gas fed to the cylinder, and that excess gas dumps into the receiver like a DI AR.  From what I've seen of the Tavor 7, the short-stroke piston doesn't extend nearly as far towards the breech as the long stroke setup (as you'd guess from the names), the gas being confined to a smaller cylinder in what you can think of as a big gas block towards the barrel (there's a push rod transferring the motion to the bolt carrier, without any plumbing for gas).  the valve adjustment knob for the gas cylinder is on the front of this block, so I'm assuming that the vent for any excess gasses is on the front of the block also, and should vent forward.  That there's a setting for suppressors on the adjustment knob also means that less gas is being tapped from the barrel on that setting, which should prevent any over-gassing to begin with.

The main differences between short and long stroke gas piston setups are that long-stroke is mechanically simpler (the piston is part of the bolt carrier group) and self-regulating (over-gassing just gets vented at the end of the piston's stroke, though as noted, that can leave a mess), while the short-stroke setup is more expensive (more parts to make) and cleaner, with the gasses confined to a smaller cylinder at the front of the weapon, and can be made adjustable with a valve at the gas port.  I guess you could make long-stroke systems adjustable with a valve as well, but I haven't seen a setup like that.

There are companies that make long stroke rifles with adjustable gas systems. My Daewoo rifle has an FAL style gas plug with the AK style long stroke bolt carrier.
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Jwill
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« Reply #10 on: November 09, 2018, 03:08:27 AM »

I personally think that short stroke gas systems are superior for two main reasons one less reciprocating mass and the second is that the gas is vented outside of the receiver. My tavor is the dirtiest rifle that I have ever shot my bren 805 and gas piston ar however stay very clean.
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Halmbarte
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« Reply #11 on: January 02, 2019, 04:50:58 PM »

The 556 Tavor does have a gas relief hole that vents high pressure gas once the gas piston has started to move back. It's located under the gas tube almost at the rear.

That said, how much gas fouling gets into the receiver depends on the design. Many designs deliberately unlock the bolt while there is still significant gas pressure in the bore. The pressure is used to accelerate the bolt backwards for reliability and/or to increase cyclic rate.









H
« Last Edit: January 02, 2019, 05:09:41 PM by Halmbarte » Logged
Tvfreakarms
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« Reply #12 on: January 02, 2019, 05:50:04 PM »

That's 1 of the things I don't like about the tavor piston system.  Blowing the excess gases back inside the rec. Why design it that way. Same goes for the for the MDR.

Lazy asses 😂. I rather have the excess gases go out and away from the shooters.
Bit that's my 2 cents.

Does anyone know if the tavor 7 has the excess gases go out and away from the shooters?

LLAP

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BullpupT
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« Reply #13 on: January 02, 2019, 06:14:30 PM »

The AR series shoot gasses directly into the bolt carrier. It’s done on purpose, let’s not forget that carbon is a lubricant. Eugene Stoner knew exactly what he was doing.

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Tvfreakarms
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« Reply #14 on: January 02, 2019, 07:31:08 PM »

The AR series shoot gasses directly into the bolt carrier. It’s done on purpose, let’s not forget that carbon is a lubricant. Eugene Stoner knew exactly what he was doing.
I c. But the whole rec doesn't need all that carbon. Obviously a piston system is going to have carbon build up regardless. But to have the whole inside of the rec to be gunked up is not fun to clean. Especially if u cant get inside the rec system easily.

But there a good lubes out there that will work good.


LLAP

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Halmbarte
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« Reply #15 on: January 02, 2019, 07:45:46 PM »

That's 1 of the things I don't like about the tavor piston system.  Blowing the excess gases back inside the rec. Why design it that way. Same goes for the for the MDR.

Lazy asses 😂. I rather have the excess gases go out and away from the shooters.
Bit that's my 2 cents.

Does anyone know if the tavor 7 has the excess gases go out and away from the shooters?

LLAP



The gas vent shown above is on the ‘dirty’ side of the receiver in font of the dirt guard that blocks debris from getting into the action.

A short stroke gas system would be more complex, and the Tavor is rather ruthlessly engineered to be simpler than an AK.

H
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Tvfreakarms
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« Reply #16 on: January 02, 2019, 07:53:21 PM »

That's 1 of the things I don't like about the tavor piston system.  Blowing the excess gases back inside the rec. Why design it that way. Same goes for the for the MDR.

Lazy asses 😂. I rather have the excess gases go out and away from the shooters.
Bit that's my 2 cents.

Does anyone know if the tavor 7 has the excess gases go out and away from the shooters?

LLAP



The gas vent shown above is on the ‘dirty’ side of the receiver in font of the dirt guard that blocks debris from getting into the action.

A short stroke gas system would be more complex, and the Tavor is rather ruthlessly engineered to be simpler than an AK.

H
The tavor 7 is a short stroke system.
And there are other brands of rifles that are short stroke. You already knows this. But they seem to work fine for the most part.
Some has been battle tested.
Couldn't a short stroke system made simplier?

LLAP

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Halmbarte
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« Reply #17 on: January 02, 2019, 10:49:01 PM »

I was referring to the original 556 Tavor and its long stroke gas piston. I haven't seen any details of the Tavor 7's gas system. A short stroke system is pretty much always going to have a additional part (separate gas piston) and frequently as gas plug or regulator (although a long stroke system can have a gas regulator, like on the BREN). As an example, the AUG has 3 parts in it that just aren't present on the 556 Tavor: Gas regulator, gas piston, and the gas piston return spring.

After having shot the AUG and Tavor at our local rifle match for a while, my take is that the AUG's short stroke gas system is more complex and offers more opportunities for the user to lose parts in the field. The up side to those extra parts is that the AUG has an adjustable gas regulator, plus the end of the piston offers a place to split the action to accommodate the quick change barrel.

Which is better depends on what you consider more valuable: no small parts to lose or flexibility.

H
« Last Edit: January 02, 2019, 11:35:02 PM by Halmbarte » Logged
Tvfreakarms
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« Reply #18 on: January 03, 2019, 01:56:23 AM »

I was referring to the original 556 Tavor and its long stroke gas piston. I haven't seen any details of the Tavor 7's gas system. A short stroke system is pretty much always going to have a additional part (separate gas piston) and frequently as gas plug or regulator (although a long stroke system can have a gas regulator, like on the BREN). As an example, the AUG has 3 parts in it that just aren't present on the 556 Tavor: Gas regulator, gas piston, and the gas piston return spring.

After having shot the AUG and Tavor at our local rifle match for a while, my take is that the AUG's short stroke gas system is more complex and offers more opportunities for the user to lose parts in the field. The up side to those extra parts is that the AUG has an adjustable gas regulator, plus the end of the piston offers a place to split the action to accommodate the quick change barrel.

Which is better depends on what you consider more valuable: no small parts to lose or flexibility.

H
Oh I c. Is was would be nice if they made a short stroke with 1 piece if possible.
The tavor 7 is a short stroke FYI.

LLAP

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Halmbarte
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« Reply #19 on: January 03, 2019, 12:35:45 PM »

I'm not sure if a short stroke gas system with one piece is possible, I can't think of any examples.

W/o having a gas plug in front you need something to keep the piston from blowing out the rear of the gas cylinder. You could use  a stop, but that stop has to be removable to assemble the piston and to remove it for cleaning, so extra parts are needed.

With a gas plug in front, you're back to extra parts.

Long stroke does have advantages too. You get to add the mass of the gas piston to the bolt carrier mass, improving the BCG to bolt mass ratio, which helps with reliability. As mentioned before, it's simpler, which has intrinsic advantages too.

I'd really like to see how IWI implemented the Tavor 7 gas system to see what they thought were good design compromises. After all, all designs are a compromise, great designs (like the Tavor) come from getting the compromises right.

H
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