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Posted: 8/4/2016 8:14:58 PM EDT
| I tried doing a search for this but it came back with no results found. I'm confused about the difference between mid length gas system and carbine length. I'm putting a 16" LaRue Stealth barrel on a build and can't find the specs stating whether it's a mid length or carbine. I want to make sure I order the correct buffer and spring. |
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Great, that was my preference. Could someone point me somewhere that explains the difference? Thanks in advance. Quoted:
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The 16in Larue Stealth barrel is mid gas. Great, that was my preference. Could someone point me somewhere that explains the difference? Thanks in advance. The simple answer is that a carbine gas system is shorter than a mid gas system. If the gas port is close to being sized correctly, the mid gas barrel should have a slightly softer felt coil.. |
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The simple answer is that a carbine gas system is shorter than a mid gas system. If the gas port is close to being sized correctly, the mid gas barrel should have a slightly softer felt coil.. Quoted:
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The 16in Larue Stealth barrel is mid gas. Great, that was my preference. Could someone point me somewhere that explains the difference? Thanks in advance. The simple answer is that a carbine gas system is shorter than a mid gas system. If the gas port is close to being sized correctly, the mid gas barrel should have a slightly softer felt coil.. Is the length a standard spec? |
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The length of the gas system. Carbine length, Mid length, Rifle length, etc. Are they standard spec lengths? Quoted:
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What length? The length of the gas system. Carbine length, Mid length, Rifle length, etc. Are they standard spec lengths? Yes, they should be. |
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Thank you all for the replys. This is exactly what I was wanting. Changing the subject though, does the search feature for the forum work? I haven't been able to do a search and it return any matches. Just wondering. I think it is kind of like a slot machine but instead of putting coins in you put the code in... and get nothing out of it. AKA I haven't figured it out yet either. |
| Choosing the optimum length gas system is important for correct dwell time. The optimum dwell time is important for quickest follow up shots. The carbine length gas system was originally developed for the M4 with a 14.5" barrel. The 16" barrel was created for commercial sale, but never used in the Armed Forces. Using a mid length gas system with a 16" barrel, actually correlates with the "Milspec" M4, and it's 14.5" barrel with carbine gas system. |
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Changing the subject though, does the search feature for the forum work? Quoted:
Changing the subject though, does the search feature for the forum work? It sorta does but IIRC some functions are not enabled for free members. Try google with "site:ar15.com" in the search string. Quoted:
I want to make sure I order the correct buffer and spring. Buffer and spring is not dictated by the gas system, although certain weights may tend to be better options depending on the characteristics of particular barrel & gas system setups. |
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I have better luck when I use an outside search engine like google or bing and include AR15.com in the box like: "midlength or carbine gas AR15.com build it yourself" you're doing it wrong... try this "site:www.ar15.com midlength or carbine gas build it yourself" |
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you're doing it wrong... try this "site:www.ar15.com midlength or carbine gas build it yourself" Quoted:
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I have better luck when I use an outside search engine like google or bing and include AR15.com in the box like: "midlength or carbine gas AR15.com build it yourself" you're doing it wrong... try this "site:www.ar15.com midlength or carbine gas build it yourself" It worked just fine for me ;-) |
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Take a longer look at the pic above.
We talk about how long the gas length is on the barrels but that's not the point. It's where the port location is from the muzzle. The correct dwell time is about five inches from the end of the barrel. It's a timing issue, and the length of the tube is what it is. That is why the gun makers came up with a non milspec "mid length" for gas on the 16" barrel. It's actually correct to the operation of the gun and adheres more to the engineering of the gas system dynamics than carbine length on 16". They had to do that because carbine length taps early into a higher pressure and it causes early opening of the bolt and higher cycling speeds. Both cause malfunctions and increase stress on the bolt. It also causes the bolt to literally bounce off the extension and unlock, which is not good if the firing pin hit the primer just as it locked up - now it's opening when the powder train is going off and partial extraction is going to be ugly. You time from the muzzle. Not the chamber. The AR15 does not have compensating gas valving to control the pressure wave and moderate it for the action like a shotgun - note that testers like to abuse them with light bird and magnum goose for testing to see if the engineers got it right. With the AR the standard is NATO milspec ammo and that is loaded to just one standard pressure. So the port is located back from the muzzle where that one standard pressure and the unlocking timing are the single known point. Same reasoning behind intermediate - it's more correct and another non milspec gas length done right for 18". If you want it to run right and the pressure correct for the barrel length then you tap back 5" from the muzzle on rifles and you get the best results. Switch it up for some reason and you live with adjusting port diameters, buffer weights, spring pressures, etc because you are now the engineer. You get to figure it out. Which goes to Crane stating that the 10.5" SBR may need up to an H3 buffer to run reliably. It's not capable of having 5" back from the muzzle as timing would be too early and gas pressure nearly double. There is likely a math expression which would state the operating curve of gas port vs barrel lengths for the AR in 5.56 - and other calibers - but Colt and others haven't put that out there for one simple reason - it's their engineering and proprietary. You don't give away business secrets. So we play the gas length game trying to understand it. |
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We talk about how long the gas length is on the barrels but that's not the point. It's where the port location is from the muzzle. The correct dwell time is about five inches from the end of the barrel Quoted:
We talk about how long the gas length is on the barrels but that's not the point. It's where the port location is from the muzzle. The correct dwell time is about five inches from the end of the barrel No. If you want it to run right and the pressure correct for the barrel length then you tap back 5" from the muzzle on rifles and you get the best results. No. Shorter gas systems with higher port pressures should have less dwell. |
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