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AR-15 gas system
7.62x39Lover
Member Posts: 3,939 ✭✭✭
I have heard that carbine length gas systems on AR-15 carbines (M4) run so much evergy through them that they shorten the life of the rifle. I've heard that the standard length gas systems in the 20" rifles are better from that standpoint. That they are easier on the rifle.
I heard that now they are selling carbine length barrels with standard length gas systems (dissipator barrels).
Are the dissipator barrels the way to go? Do they work well? Is it too early to tell? Is it silly to even worry about gas system length in terms of the useful life of your rifle? Now that I think about it, I do not know if I like the idea of the gas system "leaching off power" so close to the muzzle. What do you guys think?
I heard that now they are selling carbine length barrels with standard length gas systems (dissipator barrels).
Are the dissipator barrels the way to go? Do they work well? Is it too early to tell? Is it silly to even worry about gas system length in terms of the useful life of your rifle? Now that I think about it, I do not know if I like the idea of the gas system "leaching off power" so close to the muzzle. What do you guys think?
Comments
EDIT Disappator barrels are nothing new they've been around for years. It is probably the look and the longer sight radius on the 16 inch barrels, that makes them popular.
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Technically, the design used on most AR's is called a "gas impingement" system. Some folks have developed a "piston" system to keep the hot, dirty gases away from the action, & these models are readily available if you choose. However, the improvement is mostly theoretical, & it is unlikely to reduce the wear on moving parts.
http://www.americanrifleman.org/articles/ar-gas-piston-gas-impingement/
Neal
If this really concerns the OP, the use of a pigtail gas tube might be in order. Just my observations, but if you're not jerking case rims off, you're probably OK. I think the Dissapator is a means of extending sight radius on carbine length barrels and not really a factor unless you need that feature. Porting would likely need some tweeking with the gas port that close to the muzzle.
I have heard that carbine length gas systems on AR-15 carbines (M4) run so much evergy through them that they shorten the life of the rifle. I've heard that the standard length gas systems in the 20" rifles are better from that standpoint. That they are easier on the rifle.
Either system will last well through tens of thousands of rounds, to the point where parts replacement costs become negligible compared to ammo costs.
quote:
I heard that now they are selling carbine length barrels with standard length gas systems (dissipator barrels).
The Bushmaster "dissipator" isn't new. Its been around for at least several years now, and although it LOOKS like what you are describing, in fact, its something different.
The gun is a carbine, but using a low profile gas block hidden under a rifle-length handguard, and then has the sight base moved out, onto what amounts to a "fake" gas block. See here:
The point is to give you a rifle-length iron sight radius on a carbine sized-gun. A second point is that the longer handguard covers the barrel more, plus allows more "real estate" to hang more (useless) crap off your gun.
Since the "guts" are a standard carbine with a standard carbine-length gas system, the "Dissipator" doesn't improve or decrease reliability or wear over a regular carbine.
quote:Are the dissipator barrels the way to go? Do they work well? Is it too early to tell? Again, the BARREL is the same as a regular carbine. The main difference is how the sights and handguard are arranged.
Whether or not this particular setup offers any advantage over a variety of currently available low-gas block and free float barrel systems is debatable, but some people do like this arrangement. It comes down to what you are trying to accomplish and personal taste.
quote: Is it silly to even worry about gas system length in terms of the useful life of your rifle? I don't think its silly to ask the question. Just realize that carbines do normally have a long service life.
quote:
Now that I think about it, I do not know if I like the idea of the gas system "leaching off power" so close to the muzzle. What do you guys think?
As mentioned, virtually EVERY centerfire rifle-caliber semi-automatic gun works this way (including the SKS and Kalashnikov rifles that you "love"!). They all bleed off some miniscule (and functionally insignificant) amount of gas and use it to operate the guns' action.
I wouldn't worry about that either.
Edit: The "problem" that many people DO worry about with the direct gas impingement system of the "standard" AR-15 (vs piston-driven ones) is that the gas bled off to cycle the gun blows directly into the action, depositing carbon and other dirt there. The typical phrase for this is that the gun "poops where it eats".
How bad of a problem this is, is debatable, and then again, you open up another (endlessly debated) argument over which is "Better" the traditional direct impingment "gas" AR-15 or the newer "piston" models. Without opening up THAT can of worms, I'd say the following: While piston-driven guns definitely do offer some advantages, there are also some disadvantages (higher cost, harsher recoil, etc). The DI gas system has been around for a LONG time, it is tried and true, and I think for *MOST* casual/recreational users (which means most users period) its "good enough" to the point where they probably won't see any functional advantage with a piston-based system.
The "carbine length vs. mid-length vs. rifle-length vs. piston" debates are the newest form of the ".270 vs.30-06, lever vs. bolt, DA auto vs single action auto, or 1911 vs wondernine" debates of old... we gotta give 'riters sometin' to 'rite about, and makers sometin' to make. In my (somewhat limited experience) with semi and full auto AR's (and newer M-4's) over the past 20+ years, 95% of it is just wind.
Enjoy your gun! Clean it when it needs it, don't burn through mag after mag after mag on full auto, and you'll be handing it down to your grandkids long before it wears out.
The best line I have read in a long time.
As usual, BTS adds some good insight. The Dissipator is basically a rifle length sighting plane on a shorter barrel. I like the idea, and will sooner or later add one to the stable.
If you like the idea of a longer sight radius on a shorter gun, I'd urge you to consider a low-profile gas block under a free-float handguard instead of the true "dissipator" system.
I believe armilite's picture above shows this. Its also, by the way, how I have my own personal AR-15 set up (basically a stock carbine with solid stock, folding sights and free float handguard).
Its a more modern rendition of the "dissipator" system, with a few potential advantages.
The free float handguard/barrel should offer a little better intrinsic accuracy. It will also be less resistant to distorting your point of impact from barrel flexing if you rest the handguard on something while shooting. Typically people put folding front sights on their free-float barrels (again, you can see this in armilite's picture), and those are both more snag resistant and won't block your sighting picture if using optical sights. Also a free float setup "may" offer better overall balance/weight distribution to the gun.
quote:
The "carbine length vs. mid-length vs. rifle-length vs. piston" debates are the newest form of the ".270 vs.30-06, lever vs. bolt, DA auto vs single action auto, or 1911 vs wondernine" debates of old... we gotta give 'riters sometin' to 'rite about, and makers sometin' to make. In my (somewhat limited experience) with semi and full auto AR's (and newer M-4's) over the past 20+ years, 95% of it is just wind.
I'd largely agree with that. Any of these systems can work fine, so long as they're set up correctly, and you know how to operate and maintain them.
Most of the differences come down to niche applications and/or personal preference. If you're not stressing your particular gun to its absolute limits (ie running hundreds to thousands of rounds sequentially without cleaning, in harsh environments), or using non-standard ammo, I doubt you'll see any functional difference.
For Charliemeyer. You've probably seen this image, right?
Along the same lines:
It gets to be a parody, but I've seen guns with quad rails, on which are mounted scopes with their OWN quad rails!
For me its simple: Iron sights, *maybe* optical sight too. .done. I want to minimize the amount of "cheese grater" on my gun!
If you're a "door kicker" or want a urban/house defensive rifle, a flashlight makes sense. If you're running an AR-10 or varminter type gun, OK, I could see a bipod. *Some* people like a vertical foregrip. . .OK. But how many rail slots do you really need for these things?