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Author Topic: Short stroke Vs long stroke  (Read 1046 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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