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Posted: 9/22/2021 1:09:44 AM EDT
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Each time the gun cycles in an AR15, the gas key retreats with the bolt, disconnecting from the gas tube, while the gas tube remains fixed to the gas block. WHAT IF you inverted the relationship and fixed the gas tube to the gas key on the bolt, so every cycle it pulled the gas tube away from the gas key? Would this have any real world affect on barrel harmonics/accuracy/things I don't understand? I've got some wild ideas in coming down the pike and they kind of hinge on this flipping relationship 
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The system is designed to keep the back of the gas tube steady so the gas key can slide right back into place. If you want to accomplish what you're suggesting, you'll need some kind of collar or tube or mechanism in place to guide the tube back into the gas block reliably, not unlike the ak-47 gas tube that guides the piston back into place. That will complicate things on the front end and have a lot of compatibility issues with handguards, etc Probably possible, seems like a lot of unnecessary trade-offs though. |
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Originally Posted By Daggertt: The system is designed to keep the back of the gas tube steady so the gas key can slide right back into place. If you want to accomplish what you're suggesting, you'll need some kind of collar or tube or mechanism in place to guide the tube back into the gas block reliably, not unlike the ak-47 gas tube that guides the piston back into place. That will complicate things on the front end and have a lot of compatibility issues with handguards, etc Probably possible, seems like a lot of unnecessary trade-offs though. Ya I've taken the handguard and rod guide into account. What I was initially thinking was keeping it a true hollow gas tube but just 'fixing' it into the key, and running a gas tube that extends 4" out through the gas block back to account for the bolt travel so it stays inside the gas block and never leaves it. The 4" of extra gas tube would be solid so no gas would be going the wrong direction either.. |
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Originally Posted By thelastfoiter: Ya I've taken the handguard and rod guide into account. What I was initially thinking was keeping it a true hollow gas tube but just 'fixing' it into the key, and running a gas tube that extends 4" out through the gas block back to account for the bolt travel so it stays inside the gas block and never leaves it. The 4" of extra gas tube would be solid so no gas would be going the wrong direction either.. Where do the gasses go then? If the tube is connected to the carrier at one end and the gas block at the other and never separates from either then where does the pressure go? |
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Originally Posted By PennyForTheGuy: Where do the gasses go then? If the tube is connected to the carrier at one end and the gas block at the other and never separates from either then where does the pressure go? LOL good question! Doesn't most of it go out the barrel and if that's not good enough couldn't I just put a small hole in the back of the gas key after the angled bit where the backpressure comes from? |
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Originally Posted By thelastfoiter: couldn't I just put a small hole in the back of the gas key after the angled bit where the backpressure comes from? Wouldn't the gas just go through the hole without imparting enough force to cycle the action? But even if it worked, at that point you're still venting gas into the action so why bother pinning the gas tube to the carrier in the first place? |
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Originally Posted By Flonominal1: OP, check out the ZM Weapons LR300 and the Para USA TTR, they used a long gas tube/key that separated from the block instead of the carrier. They also incorporated the recoil spring into it, removing the need for a buffer tube, really interesting design https://i.imgur.com/2vjX9Lj_d.webp?maxwidth=640&shape=thumb&fidelity=medium ITS LIKE YOU'RE READING MY MIND WTF That's reassuring though, someone has made something like what I'm going for work out |
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Originally Posted By thelastfoiter: Each time the gun cycles in an AR15, the gas key retreats with the bolt, disconnecting from the gas tube, while the gas tube remains fixed to the gas block. WHAT IF you inverted the relationship and fixed the gas tube to the gas key on the bolt, so every cycle it pulled the gas tube away from the gas key? Would this have any real world affect on barrel harmonics/accuracy/things I don't understand? I've got some wild ideas in coming down the pike and they kind of hinge on this flipping relationship No advantage. |
"Audemus jura nostra defendere"
QC Doktor...soldier, scholar, funnyman, raconteur
Joined:
Feb 2001
Posts:
29211
EE: 0% (0)
AL, USA
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Originally Posted By thelastfoiter: WHAT IF you inverted the relationship and fixed the gas tube to the gas key on the bolt, so every cycle it pulled the gas tube away from the gas key? Would this have any real world affect on barrel harmonics/accuracy/things I don't understand? Oh, boy! MORE reciprocating mass - just what the doctor ordered. Yes it would change some harmonics, and make servicing the BCG a PITA, with that long, fixed gas tube sliding in and out of a 3-4" collar around the gas block. |
"The only real difference between the men and the boys, is the number and size, and cost of their toys."
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NRA Life, GOA Life, CSSA Life, SAF Life, NRA Certified Instructor
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The ZM weapons doesn't change how the gas system operates technically. It's still a gas tube with a gas key with the gas tube fixed in the gas block. They just extended the gas key a LOT, so that the actual gas tube coming from the gas block is short and the gas key extends all the way up almost to the gas block. They also chopped the BCG, so there's actually not any additional weight/mass. Also extra vents for the extra gas. It's like they took everyone's concerns from this thread and addressed them.... 25 years ago. Attached File http://firearmsandtraining.gunetools.com/2009/01/z-m-weapons-lr300-take-down-details.html  LR300 Internals |
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Originally Posted By GriswoldGuns: There is a member here that made something like this and posted threads on it years ago. I am bad with names but I think it was @RDTCU or something similar. Yep (see avatar) back in like 2008. What i built was basically just a beefed up version of the ZM LR300 posted above, with the addition of a forward charging handle. It makes things handy and let's you fire with a folded stock, but it is more or less a novelty given today's options. Recoil is relatively soft, i used a delrin block and fat o-ring to absorb the impact at end of stroke. I put a ton of nasty stuff through it back in the day, to the point of smoking, and the only issue i had was stripping laquer/poly coated steel cases from certain tight mags. Didn't have the bolt overstroke and mass to break it loose when things got dirty. Attached File Attached File Attached File |
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Originally Posted By Daggertt: The ZM weapons doesn't change how the gas system operates technically. It's still a gas tube with a gas key with the gas tube fixed in the gas block. They just extended the gas key a LOT, so that the actual gas tube coming from the gas block is short and the gas key extends all the way up almost to the gas block. They also chopped the BCG, so there's actually not any additional weight/mass. Also extra vents for the extra gas. It's like they took everyone's concerns from this thread and addressed them.... 25 years ago. https://www.ar15.com/media/mediaFiles/435611/Screen_Shot_2021-09-22_at_11_59_48_AM_pn-2100240.JPG http://firearmsandtraining.gunetools.com/2009/01/z-m-weapons-lr300-take-down-details.html  https://www.youtube.com/watch?v=0fmY13xYUkcThank you again, extending the gas key (partially) I think is exactly the idea I needed to hear. That video is excellent as well. |
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Originally Posted By RDTCU: Yep (see avatar) back in like 2008. What i built was basically just a beefed up version of the ZM LR300 posted above, with the addition of a forward charging handle. It makes things handy and let's you fire with a folded stock, but it is more or less a novelty given today's options. Recoil is relatively soft, i used a delrin block and fat o-ring to absorb the impact at end of stroke. I put a ton of nasty stuff through it back in the day, to the point of smoking, and the only issue i had was stripping laquer/poly coated steel cases from certain tight mags. Didn't have the bolt overstroke and mass to break it loose when things got dirty. https://www.ar15.com/media/mediaFiles/173511/DSCN0343_jpg-2100477.JPG https://www.ar15.com/media/mediaFiles/173511/IMG_20130704_231500_079_jpg-2100478.JPG https://www.ar15.com/media/mediaFiles/173511/IMG_20150526_181651_432_jpg-2100479.JPG Woah now we're cooking. Could I get some more details or pics please of your end of stroke impact dampening setup as well as how you implemented your gas system? Would be a HUGE help and cool guns! |
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Originally Posted By thelastfoiter: Woah now we're cooking. Could I get some more details or pics please of your end of stroke impact dampening setup as well as how you implemented your gas system? Would be a HUGE help and cool guns! Cup to fill buffer tower, delrin disc with fat 1" o-ring behind it. Countersunk screw to retain it without contacting firing pin on stroke. Attached File |
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Originally Posted By thelastfoiter: Ya I've taken the handguard and rod guide into account. What I was initially thinking was keeping it a true hollow gas tube but just 'fixing' it into the key, and running a gas tube that extends 4" out through the gas block back to account for the bolt travel so it stays inside the gas block and never leaves it. The 4" of extra gas tube would be solid so no gas would be going the wrong direction either.. ZM did this with the LR-300 design in the 90s. |
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Originally Posted By JoshNC: ZM did this with the LR-300 design in the 90s. Originally Posted By JoshNC: Originally Posted By thelastfoiter: Ya I've taken the handguard and rod guide into account. What I was initially thinking was keeping it a true hollow gas tube but just 'fixing' it into the key, and running a gas tube that extends 4" out through the gas block back to account for the bolt travel so it stays inside the gas block and never leaves it. The 4" of extra gas tube would be solid so no gas would be going the wrong direction either.. ZM did this with the LR-300 design in the 90s. |
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