Question for the AR15 gurus on the forum....Dissipator?

[shooter]

I picked up a stripped lower this weekend to do my first build. I have recently discovered the "dissipator" version. I'd never seen it before, but I like the concept. Full length gas system and sight radius in a carbine length. Plus I think it looks cool. Are there any advantages besides the sight radius? Is the gas system more reliable than a carbine length system? I've also heard people rave about a mid length gas system on a carbine length barrel. Why are the longer gas tubes more reliable than the carbine length versions?

Here is how I'm thinking I want mine to end up looking: http://www.bushmaster.com/catalog_xm15_BCWA3F16DMOE.asp

[sore shoulder]

The problems claimed to be solved by the mid length gas system do not exist, if they did, the miltary and Colt would have addressed it long ago. Both Hobie and I have commented on this and both of us have seen way more carbines getting extreme use and abuse than most people ever dream of, and Hobie's experience eclipses mine. What it does do is give your gun a non standard gas tube. The full length site and gas tube on a carbine is a good idea IMO just for the longer sight radius.

[AJMD429]

I don't think you're getting a 'standard' length gas system, though perhaps in theory it is better (less shock and wear) than the 'carbine' length one.

Here's a prior thread on the topic - http://www.levergunscommunity.com/viewt ... =1&t=39305

Of course the 'piston' systems have some advantages too, but for those of us who won't shoot tens of thousands of rounds through our AR's, or use them for life-and-death missions in harsh environments, ANY of them probably will be just fine.

One simple 'fix' for the 'carbine' gas systems, is just to get an adjustable gas tube - the one I have on a shorty can be adjusted to let so little gas into the system it functions as a single-shot. Increase the gas 'allowance' until it just functions reliably, then maybe a bit more, and you have a functioning gun with no 'extra' gas back into the action. Dunno if it matters that much, but it's one 'solution'...


http://www.midwayusa.com/product/297939 ... tube-ar-15

They also make adjustable gas-blocks in various (sight, no sight) configurations:

http://www.midwayusa.com/product/743543 ... less-steel

[sore shoulder]

AJMD, no offense intended to you with the following remarks.

Hobie's comments bear reposting here. My own experiences as a current NCO and range safety in a light Infantry unit mirror Hobie's experiences below. The piston is a "solution" for a problem that simply does not exist except in the minds of keyboard commandos and in the ads of people selling the parts. What a piston does do is configure your rifle with non standard proprietary parts that add weight to the rifle and make it less accurate. The problems allegedly associated with a carbine gas tube do not exist. I have seen more rounds fired through M4's in one weekend of high tempo live fire training than the next ten guys put together will see their entire lives. The M4 carbine just keeps running.

Simply put, save your money and buy a quality true milspec AR and you will probably never have an issue, nor will those who inherit the gun. If they do, there is an endless parts supply chain that will last for generations.

If you want to go the frugal route and buy a shooter grade or build your own from budget priced kits, expect it to have issues. I've built and helped build several and seen a lot of the problems. Gas keys coming loose from improperly staked screws, trigger pins coming out because either the pin or the hole aren't to spec, extractors failing from non spec springs, failed extraction due to out of spec chamber, gas block pins misaligned in the front sight and a few others I forget. Clint Black of Thunder Ranch combat carbine course fame has stated that the most reliable carbine he sees is a Colt, the home builds and cheaper carbines tend to have issues when going through a thousand rounds in a day.

There's a reason for this, very strict quality control that others simply do not have. There are a few companies who have begun producing true milspec rifles, but all their rifles are not true milspec. If you think it doesn't matter, you simply don't really know or understand the difference and are doing others a disservice by going around saying so. I'm guilty of doing so myself. My experiences have proven me wrong.

I have taken the time to say all this because someday someones life may depend on that rifle, whether yours or a loved one. Why take chances.

I wanted to add a bit of my personal experiences.

As most of you know, there were a couple of different mfgs out there in the A1 age who weren't Colt. There were even still the experimental guns in the BCT companies. I used to be a range safety and then range officer for my brigade and we would sometimes have to expend (were ordered to expend) large quantities of ammo. Usually we only had a couple of guys and their weapons. I have seen M16A1s and A2s go through 10-20 magazines rather quickly, in hot and cold weather, in wet and dry, correctly lubed and not, some after having fired blank ammo (which is filthy as noted above). The guns simply didn't fail. They were still accurate afterwards. The standard was not less than 4 MOA and I can't remember having ever fired or seen a gun that shot less than 2 MOA, ever.

The guns held up in other ways as well. Some of my guys could break an anvil with a rubber mallet but they didn't break their rifles.

It seems to me that the problem (if there ever is one) is with the deliberately sub-standard parts, not the average or high quality components. Sure, you will have a bad part in any production run but these seem few and far between to me.

In the shop, every problem we have seen with the ARs is directly attributable to ham-handed modifications by the owner. Screwed up gas tubes, incorrectly assembled trigger assemblies and incorrectly installed buttstocks leading the way.

[RustyJr]

I own a Bushmaster AR15A2 20" HBAR. I personally prefer the 20" over the 16" because of the added velocity. While many may disagree (this is personal opinion and is based only on speculation and no real life experiance) I try to stick with a 20" barrel and prefer 55 grain rounds. My thought is that the 5.56/223 was designed to operate using that combination (barrel length/bullet weight). No it wont shoot as well at 500 yards as a 62 or 69 grain load but out to the distance it was origanally designed to be used at, 300 yards and under it will work fine. If we are honest with ourselves the chances of us using them past 100 yards for HD are slim to none. Another thing about mine is that mine is just a plain jane rifle with no frills. Less to go wrong with it and M1 Garands and M1As were used for ALOT of years without all the dodads and did just fine. One thing that I will add to mine is a good three point sling and a flashlight. Other than that I am going to try and stay simple. I agree with Hobie though . . . I think everyone should have an AR.

RustyJr

[Hobie]

I hope everyone realizes that there are others with more combat experience with the AR than I, since I had no COMBAT experience with the system. However, I think I had a LOT of training experience. I just want to be clear on that.

Sometimes, in every field of manufacture, there is a lot of pressure to produce something new and improved in order to market an item and sell an item without regard to actual benefit to the end user. Assuming the quality of the parts is the same or at least adequate (including assembly of said parts such as the bolt carrier mentioned by Sore Shoulder), and the gun functions, then the configuration is a personal preference. Only the end user knows which best suits.

[MrMurphy]

I have no combat experience per se as I never ended up pulling the trigger. Had a lot of near misses, but never went hot.


The midlength does give a gentler recoil impulse and somewhat on the wear and tear, but it isn't any more reliable particularly than the carbine length, it just helps cut down on parts wear over time.


The Dissipator is a good idea for iron-only guys, and before the Aimpoint was issued it did make sense.

These days a 16" barreled carbine with a 12 or 13" freefloat tube will accomplish the same thing with irons.

[Mich Hunter]

Not tooting my own horn, but I am very familiar with the AR platform. On the dissy uppers. You are getting a carbine length gas system with a rifle length sight radius. That is it. Cool looking? Sure. More hand guard space for rails and such? Sure. If you ever watch the open class target shooters when using modified AR's, their sight radius is increased further.

Gas Pistons--

This is not new technology. It's been around since the turn of the last century. Most all major battle rifles are gas piston operated. AK's, FAL's M14's, M1 carbines, Garands etc. However, it seems to be the latest craze. Does it solve an age old problem? Sort of. The HK 416 really started it off in the DOD. Now the Army is starting (budget cuts maybe)to convert their M4's over to piston. Reason?? With the piston system in the AR, you are not getting the hot gas and grime in and around the bolt and upper receiver. All that stuff heats up and forges itself to the bolt and barrel extension. I see it daily as I train roughly 60 per week on the M4/M16A2. We put over 1 million rounds down range annually out of less than 100 M4's/M16's. The piston system does run cooler and cleaner. It also does not add weight nor effect accuracy. No doubt about that. However, the standard AR has been getting it done for years and is proven.

Quality and home builds---

If you want an AR and not over pay for it, build it yourself. It is not hard and you can do it with hand tools with exception of the barrel wrench and receiver vise support. It is easier then pressing together an AK. Trust me, I smith on these weekly and its like putting together a lego set. I disagree with others who say you will have nothing but problems. Not true at all. If you have any kind of mechanical skills, just follow a T.O. The key is to buy MIL SPEC Parts and you will not have an issue. There are a couple stuff companies out there, but most are just fine. Like I have said before, YOU PAY FOR THE NAME 90% of the time. Uncle Sam has sent me to many armorer schools and I learned the truth. The majority of the lowers, LPK and barrels are made by the same people. Mil spec is mil spec period. However, I would suggest that your lower parts kit should be made by the same company as the lower receiver. Case in point though. We bench stock every single part in the various T.O.s for M9 Beretta's to Mk19's and M2 Brownings. 98% of the replacement parts we have are made by subcontractors, not Colt,FN etc. We never have issues with QC.

Quality-- Just depends. Colts are nice, but I have seen my fair share of lemons from them. Poor assembly is one of the main issues I have had. I have pulled brand new weapons out of the box and have watch parts fall of like pistol grips and sight. But you will see issues with everyone. FN makes a very nice product, but you won't see a semi version on the commercial market. Some folks dislike DPMS, but I have never had an issue myself. Same with Bushmaster.

Personally, I am not really a fan of the AR, however it is my job to know them. They have turned into the next Winchester 94 as far as being the "American" rifle IMHO. I own more than a couple, but my Garands and M1A's get out to play more than anything.

[Lastmohecken]

I have an M4 and a Dissipator, both Bushmaster. I have had no problems with either one. I like the looks of the Dissipator, and the longer sight radius.

[AJMD429]

AJMD, no offense intended to you with the following remarks.

None taken. All I was really saying anyway was that

• a) I think the Dissipator is NOT a "full length" gas system,
  b) of the three options (full length gas, short gas, and 'piston'), none is exactly "bad"
  c) the piston one might be best for military or high-volume users (but costs more)
  d) the shorty one might put more wear on your gun (but adjustable tubes/blocks may help)

...but most of all, I agree with Hobie that "everyone should have an AR-15"

• (maybe in a perfect world, I'd substitute "M1A Scout Rifle" )

[damienph]

Well, my military experience is limited to 2 months at Ft Ord, CA (Basic), 2 months at Ft Gordon, GA (AIT) and 32 months in Mannheim, Germany as an MP. But I have shot thousands of rounds through 16", 20" and 24" ARs and have never had a problem with the gas system at any length. I like the 16" dissipator but in my experience it wasn't any more accurate than my 16" Bushmaster "shorty". I didn't see any advantage in the longer sight radius. Personally, I think that it comes down to what you like. It does look good and I wouldn't mind having one.

[olyinaz]

Some guys like the piston ARs because they clean their guns a lot and don't like 'em messy. Hey, it's their money! They should get maximum grins from spending it. Personally, I just run my AR wet and don't worry about it. But that doesn't mean I don't understand how nice it would be not to have such a filthy system. I'm just not going to pay for it.

Ruger seems to have gotten the mix right on their 1911 but they blew it on their AR in my view. Too pricey.

Best,
Oly

[Streetstar]

I like the Dissipator concept -- not that you need my endorsement, but i just recently finished up a range session with a pistol AR, a mid length AR and an old "retro" build with an M-16 upper

The "16" had an old 4x Colt style scope on the carry handle, but all others wore irons, --- shooting the mid length was the most satisfying, as i had recently kicked its scope to the curb

Groups were not brag-worthy, and the ammo i used was plinking grade stuff, but it was right in the hunt -- i liked it. It is teaching me how to use irons once again

[Hobie]

Sorry about the topic drift but I had to say that those old Colt 3X carry-handle mounted scopes were the bees' knees for my eyes. Until the first laser designators came to the field near us I even mounted it on my M16 when in the field (and sometimes at the range when I'd already qualified. Worked a treat. I can't easily see the reticules on many of the newer optical sights either due to size or color (or both).

[foxtrapper]

AJMD, no offense intended to you with the following remarks.

Hobie's comments bear reposting here. My own experiences as a current NCO and range safety in a light Infantry unit mirror Hobie's experiences below. The piston is a "solution" for a problem that simply does not exist except in the minds of keyboard commandos and in the ads of people selling the parts. What a piston does do is configure your rifle with non standard proprietary parts that add weight to the rifle and make it less accurate. The problems allegedly associated with a carbine gas tube do not exist. I have seen more rounds fired through M4's in one weekend of high tempo live fire training than the next ten guys put together will see their entire lives. The M4 carbine just keeps running.

Simply put, save your money and buy a quality true milspec AR and you will probably never have an issue, nor will those who inherit the gun. If they do, there is an endless parts supply chain that will last for generations.
Now there's some straight talk! I agree on all points! FWIW
If you want to go the frugal route and buy a shooter grade or build your own from budget priced kits, expect it to have issues. I've built and helped build several and seen a lot of the problems. Gas keys coming loose from improperly staked screws, trigger pins coming out because either the pin or the hole aren't to spec, extractors failing from non spec springs, failed extraction due to out of spec chamber, gas block pins misaligned in the front sight and a few others I forget. Clint Black of Thunder Ranch combat carbine course fame has stated that the most reliable carbine he sees is a Colt, the home builds and cheaper carbines tend to have issues when going through a thousand rounds in a day.

There's a reason for this, very strict quality control that others simply do not have. There are a few companies who have begun producing true milspec rifles, but all their rifles are not true milspec. If you think it doesn't matter, you simply don't really know or understand the difference and are doing others a disservice by going around saying so. I'm guilty of doing so myself. My experiences have proven me wrong.

I have taken the time to say all this because someday someones life may depend on that rifle, whether yours or a loved one. Why take chances.

I wanted to add a bit of my personal experiences.

As most of you know, there were a couple of different mfgs out there in the A1 age who weren't Colt. There were even still the experimental guns in the BCT companies. I used to be a range safety and then range officer for my brigade and we would sometimes have to expend (were ordered to expend) large quantities of ammo. Usually we only had a couple of guys and their weapons. I have seen M16A1s and A2s go through 10-20 magazines rather quickly, in hot and cold weather, in wet and dry, correctly lubed and not, some after having fired blank ammo (which is filthy as noted above). The guns simply didn't fail. They were still accurate afterwards. The standard was not less than 4 MOA and I can't remember having ever fired or seen a gun that shot less than 2 MOA, ever.

The guns held up in other ways as well. Some of my guys could break an anvil with a rubber mallet but they didn't break their rifles.

It seems to me that the problem (if there ever is one) is with the deliberately sub-standard parts, not the average or high quality components. Sure, you will have a bad part in any production run but these seem few and far between to me.

In the shop, every problem we have seen with the ARs is directly attributable to ham-handed modifications by the owner. Screwed up gas tubes, incorrectly assembled trigger assemblies and incorrectly installed buttstocks leading the way.

[AJMD429]

Ruger seems to have gotten the mix right on their 1911 but they blew it on their AR in my view. Too pricey.

Personally, I'd have rather they came out with heavier-barreled Mini-14 - the concept of a "miniature M-14" is still a good one.

[olyinaz]

Personally, I'd have rather they came out with heavier-barreled Mini-14 - the concept of a "miniature M-14" is still a good one.

They did do that a few years ago Doc, even heavy target barrel versions no less. They still have the gas block problem (too thin through the block) but the barrels got quite a bit heavier in general. Sadly, this has made the rifles heavier - they no longer handle like an M1 Carbine and they got noticeably more front heavy - but they also introduced 16" versions which brought the balance back to where it feels right. I really like these short barrel Minis.

Most recently they have introduced a 16", heavier barrel Mini-30 with a flash hider called the Mini-30 Tactical (because if you put "Tactical" on anything you can sell it for a 15% premium...now excuse me while I take a pull from my Tactical Coffee and blow my nose in a Tactical Wipe). I think it's the cat's pajamas and Mini's flash hider uses standard AR threads so many other flash hiders are easy options (there are some great ones out there that will thread right on). I need one. NEED mind you.

Oly

[Old Ironsights]

The piston system does run cooler and cleaner. It also does not add weight nor effect accuracy. No doubt about that. However, the standard AR has been getting it done for years and is proven.

Yep, yep & yep.

I still hate how nasty/dirty a direct impingement gun gets.

Of course, my choice of a MBR ALSO lets (a small amount) of gas back into the works (HK flutes) but unlike in a gas-gun I can shoot BP & soft lead bullets if I need to.

[MrMurphy]

And unlike an AR, a single unlucky hit to the receiver can take an HK out of action.....


Not an issue when it's issued, there's more. But for a single man, yeah....bad....

[Old Ironsights]

And unlike an AR, a single unlucky hit to the receiver can take an HK out of action.....

Not an issue when it's issued, there's more. But for a single man, yeah....bad....

Ya mean a tin-bending fall? Yah, I guess that's true, but I think I'd be out of commission long before the rifle would...

[MrMurphy]

Known some guys in the Bundeswehr, including one who's been packing a G3 (marksman variant) around Afghanistan the last couple years.

They're tough as hell, but a hit 'just right' which may not necessarily look bad can be enough to dent the receiver and disable the rifle.

When a 20+ year senior German infantry sergeant says that, you tend to believe him. He isn't fond of the G36 either.

[Mich Hunter]

When I was talking about the HK416, it is not the typical blow back. It is a piston driven AR

http://en.wikipedia.org/wiki/Heckler_%26_Koch_HK416

[Old Ironsights]

Known some guys in the Bundeswehr, including one who's been packing a G3 (marksman variant) around Afghanistan the last couple years.

They're tough as hell, but a hit 'just right' which may not necessarily look bad can be enough to dent the receiver and disable the rifle.

When a 20+ year senior German infantry sergeant says that, you tend to believe him. He isn't fond of the G36 either.

All true. But the same same if a gas tube is bent/broken/plugged etc.

It's definitely harder these days with billet rail forends, but not impossible either. I'd say either is about as likely.

[piller]

Just my 2cents worth, but as much as I hated the M16A1, it didn't fail. I did like the A2 version for its longer stock and heavy barrel. For those who like iron sights, the longer sight radius of the dissipator would be great. I do have an AR now, but not because I liked them back when. It is as accurate as the A2 was. Now, there is nothing wrong with gas impingement, nor with gas tube-operating rod systems. Both work.

[Old Ironsights]

Just my 2cents worth, but as much as I hated the M16A1, it didn't fail. I did like the A2 version for its longer stock and heavy barrel. For those who like iron sights, the longer sight radius of the dissipator would be great. I do have an AR now, but not because I liked them back when. It is as accurate as the A2 was. Now, there is nothing wrong with gas impingement, nor with gas tube-operating rod systems. Both work.

Absolutely. Just like a Glock works.

But I don't like them either.

I'll take a G3 and a 1911 any day

[cas]

You go with what you know. I've owned a lot of AR uppers, the only ones that have ever given me problems were carbine length ones. So naturally I tend to be gun shy of them.

My most recent assembly (I'm not fond of the term "build") is a dissipator type upper.

I had a "retro" CAR-15, very pre-ban… a 1968 vintage lower, one I'd "always wanted". Like so many always wanted's once I had it I wasn't overly fond of it. Mostly I didn't care for the short sight radius.



I thought I would let it go, but I still wanted a handy iron sighted upper. I so parted it out and sold it off and put together another 16" iron sight upper to be used on one of my other lowers.
A 16" "dissy" type, but with a mid length gas system. So far I'm real happy with it.

[shooter]

Cas, that bottom pic is exactly what I've got in mind. I love the Magpul furniture and the long sight radius. I saw the Bushmaster version and decided that was what I'm going to assemble. I think I'm gonna stick with the carbine length gas system though, just because I think it has become the most common.

[awp101]

A 16" "dissy" type, but with a mid length gas system. So far I'm real happy with it.

All the recent AR talk has got me thinking about trying them again and I gotta say, that one has a certain amount (the right amount?) of sexy to it...