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Author Topic: Short stroke Vs long stroke  (Read 2262 times)
Tvfreakarms
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« Reply #20 on: January 03, 2019, 01:19:59 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
That's what I read that the tavor 7 is a short stroke.  I doubt it's a 1 piece design.
I wonder why they moved away from long to the short.
And your right I think most short stroke gas at least 2 to 3 parts. I know my pof USA rifle has 3 parts.
But it would be nice if they make it 1 part and integrate the gas plug.

LLAP
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konigstigerii
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« Reply #21 on: January 03, 2019, 05:55:35 PM »

My best guess is they moved to a short stroke piston to reduce the reciprocating mass to reduce felt recoil. (similar to light weight Ar15 bgc in competition use) The Tavor has no gas adjustment, so to make it reliable, its over gassed quite a bit, and the heavy mass of the bcg would make it less sensitive to gas port pressure and crud in the receiver, perfect for general issue to the masses with no interest in firearms...no settings, reliable, albeit over gassed with excess recoil (though not excess in respect to control-ability). The Tavor 7 is seemingly marketed to those more familiar with firearms, and those willing to understand its use, so a lighter mass bcg, and gas adjustment is preferable so we can tune it to run nice and smooth. 

My X95 has a prototype gas adjustment and when tuned it runs a lot smoother... like night and day compared to stock system.

The 7 gas system probably has a few parts, but its not that many more that a long stroke piston. The Tavor has the piston head, the piston tube, a roll pin, and a pin holding the piston tube to the carrier. My ACR has a piston, return spring, and a gas plug. So while the Tavor has technically 4 parts the ACR has 3 (minus common parts such as the gas block, trunnion etc). The tavor parts are simpler but not by any long shot. So its not necessarily true that all long stroke systems have fewer parts or is simpler to make.
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Halmbarte
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« Reply #22 on: January 03, 2019, 06:29:17 PM »

Itís kind of reaching to count parts that are semi-permanently assembled like the 556 Tavors gas piston and gas piston tube as separate parts.

Since those parts canít be removed without tools Iím arguing they should be excluded from a normal parts count.

H
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Tvfreakarms
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« Reply #23 on: January 03, 2019, 06:41:25 PM »

My best guess is they moved to a short stroke piston to reduce the reciprocating mass to reduce felt recoil. (similar to light weight Ar15 bgc in competition use) The Tavor has no gas adjustment, so to make it reliable, its over gassed quite a bit, and the heavy mass of the bcg would make it less sensitive to gas port pressure and crud in the receiver, perfect for general issue to the masses with no interest in firearms...no settings, reliable, albeit over gassed with excess recoil (though not excess in respect to control-ability). The Tavor 7 is seemingly marketed to those more familiar with firearms, and those willing to understand its use, so a lighter mass bcg, and gas adjustment is preferable so we can tune it to run nice and smooth. 

My X95 has a prototype gas adjustment and when tuned it runs a lot smoother... like night and day compared to stock system.

The 7 gas system probably has a few parts, but its not that many more that a long stroke piston. The Tavor has the piston head, the piston tube, a roll pin, and a pin holding the piston tube to the carrier. My ACR has a piston, return spring, and a gas plug. So while the Tavor has technically 4 parts the ACR has 3 (minus common parts such as the gas block, trunnion etc). The tavor parts are simpler but not by any long shot. So its not necessarily true that all long stroke systems have fewer parts or is simpler to make.
Do you know if they make a prototype gas adjustment for the sar?

LLAP

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konigstigerii
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« Reply #24 on: January 08, 2019, 03:31:43 PM »

No, I have one on my X95 that I've been working on  Wink



* 20181229_144344.jpg (746.45 KB, 1960x4032 - viewed 83 times.)
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konigstigerii
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« Reply #25 on: January 08, 2019, 03:32:47 PM »

Itís kind of reaching to count parts that are semi-permanently assembled like the 556 Tavors gas piston and gas piston tube as separate parts.

Since those parts canít be removed without tools Iím arguing they should be excluded from a normal parts count.

H

That is true to a degree, but those parts still have to be engineered, spec'd, manufactured, inspected and installed.
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Halmbarte
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« Reply #26 on: January 10, 2019, 08:49:51 PM »

Simpler from a parts count perspective isn't necessarily always better.

As an example, I offer the recoil spring assembly of the AK47. It contains the dust cover latch/support, the rear tube, front rod, recoil spring, and the retainer. The assembly requires machining, brazing, and swaging steps for manufacturing.

The end result is a more complex assembly for the factory to manufacture and assemble, but the end user gets one piece that stays together, is more difficult to lose, and combines the function of the recoil spring guide, captive recoil spring, and take down latch.

H
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konigstigerii
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« Reply #27 on: January 10, 2019, 08:59:02 PM »

Exactly, kinda like the pins on an AR15 vs a HK G36, the pins on the AR are retained, so they are hard to loose, where as the HK pins, while simpler, can be easily lost in the field
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