Gas piston uppers

[nalioth]

Just thought I'd share some gun pR0n and an interesting link.

Article (http://www.armytimes.com/news/2007/02/atCarbine070219)

Gun pR0n that won't show inline here: Pic (http://www.novarata.net/abrams/2007_02_20_Hnk416.swf)

I personally do not like the direct gas impingement system, and am happy to see a "real' usability upgrade for the politically mandated animal called the M16


Edited: HELP?! Why can't we embed Flash pictures?

[pidaster]

I like that. I never did understand why the AR were still set up the way they were. I'd much rather have a piston rod.

[97th Signalman]

I have always liked the idea of a gas piston upper for an AR. It never seemed like a good idea to run the exhaust through the kitchen.

[texlurch]

Kel-tec thought the same thing on their SU-16

[okie shooter]

I like that. I never did understand why the AR were still set up the way they were. I'd much rather have a piston rod.

Stoner did it to eliminate additional moving parts from his rifle, look at an ak which everyone will say has a piston, but it moves with the bolt carrier. Thus an ak which everyone loves still allows gas to travel thur the chamber and thus poos where it eats also. Stoner just built a much shorter piston and much longer gas tube to get the gases there.

Many rifles of the era that were automatic were heavy and had super high tollerences of machineing so they would operate when built. Stoner went about working on an idea that made the rifle easier to build, with lighter materials and a lower cost of manufacturing.

[texlurch]

Stoner did it to eliminate additional moving parts from his rifle, look at an ak which everyone will say has a piston, but it moves with the bolt carrier. Thus an ak which everyone loves still allows gas to travel thur the chamber and thus poos where it eats also.

But it doesn't travel near far enough to allow the gas to vent into the chamber. The AR gas system dumps the gas into the receiver/chamber as soon as the carrier moves back.

With a chrome bolt and chamber, it is pretty much a none issue. Which Stoner did spec, but was cut by the whiz kids for cost.
They also changed his powder spec, to a much dirtier style.

[nalioth]

Stoner did it to eliminate additional moving parts from his rifle, look at an ak which everyone will say has a piston, but it moves with the bolt carrier. Thus an ak which everyone loves still allows gas to travel thur the chamber and thus poos where it eats also. The gasses in an AK exhaust out of the holes at the front of the gas tube. You can fire up dozens of magazines from an AK and not have near the crap in the receiver that you'd get after firing ONE round through an M16/AR15. The gas from the gas tube in the M16/AR15 was routed through the bolt carrier BY DESIGN. The first place it has to release is inside the receiver/bolt carrier.

[okie shooter]

But it doesn't travel near far enough to allow the gas to vent into the chamber. The AR gas system dumps the gas into the receiver/chamber as soon as the carrier moves back.

With a chrome bolt and chamber, it is pretty much a none issue. Which Stoner did spec, but was cut by the whiz kids for cost.
They also changed his powder spec, to a much dirtier style.


On travel, how tight is the gas tube on a ak gas piston, I imagine there is huge leakage in that setup,(its the impulse of the gas on the piston that causes the system to work, not like pressure in a machined piston) I would guess more slop than the area of the gas tube on an ar, remember it proably better than ten to twenty thousands slop in a ak gas tube, the tube being only sheet metal, once the piston goes back I imagine enough gas leaks by thru the tube and sight base to vent a good amount of gas thru the receiver. The gas has to go some where, some vents out the tube but I imagine some goes past the piston(it has to go some where and aint going to be easy to vent back thru the gas tap in the barrel) thus either thru the vent holes in some ak gas tubes or thru the chamber or both.

I am just thinking of how a ak gas tube is shaped but there are reinforcement that bulge the outside of the tube, far larger than the diameter of the piston, thus once the piston is moving back the expanding gas can just get around the piston and vent back thru the tube and due to the smaller diameter of the piston rod all the way back untill it screws into the bolt there is a good amount of gas comeing out thru the top of the receiver.

I imagine every automatic rifle useing gas for recoil vents thru its piston system, some more than others, why else does the back of the gas piston need cleaning, there is fowling from the products of combuston. Just some more than others. Yes stoner did it directly, but as stated he used different powders and different specifications for chrome plateing the parts, it was the army that made the changes to the rifle for economics, the army ordnance has a history of shooting its self in the foot thus why the army had its ablity to make rifles taken away from it in some ways.

[texlurch]

Oh, I imagine there is some coming past. I think the gas hole in the AK is smaller than the ID of the AR gas tube even.

But if you think about the gas travel between the two, you have some distinction.

On the AK, as soon as the gas goes into the tube, it starts the piston moving. On the AR, the entire tube fills first, then moves the bolt.

By the time all this happens, the bullet is headed out the barrel.

In the AK, you have the vent holes in the gas tube. In the AR, you have the open end in the chamber. Path of least resistance, the majority of the gas will follow the bullet out the muzzle.

Volume for volume, I think you have more crap dumping into the chamber and receiver on the AR.

[okie shooter]

In some ways, if the army hadnt jacked with the powders used and recomended for the rifle, the huge black eye that the rifle got in vietnam might have never happened, the fact they didnt issue cleaning kits with them was even worse. I guess there are teathing problems with new rifle systems, thus even the venerable garand rifle had changes from its first introduction but luckly there was more time before it had to become battle tested in WWII. I imagine if the orginal gas system had gone to war we would have had issues with that rifle too.(can you imagine the first time your rifle bumped into something in battle by muzzle and it failed to function due to problems with the orginal gas trap system vs the direct gas feed)

I imagine the ammo we toss thru our aks and sks is alot dirter than what most folks and even the army now feeds their ar/m-16 rifles. The ar was designed in mind with newer power formulations. Remember the round used in the M-1 rifle, while stoner was working his rifle(actually the ar-10 was the orginal rifle for 30 caliber I think he started with the 300 savage cartriage) system was fifty years old or so, most of the standard rounds of the early fifties were adopted at that point or even earler(the 7.62x39 wasnt quite standard but was like the 8mm kurtz new ideas in ammo) Thus the the standard ammo of the day was just one or two adoptions removed from black powder loadings(30-40 krag, then 30-03 springfield, so just fourteen years from the change from black powder)

A side note, the krag though the adopted standard rifle of the spanish american war, wasnt available in enough numbers so troops went to battle with 45-70 rifles too, but what impressed the army was the spanish mausers, which some folks think spured the change to the 03 and 06 springfield rifles.

[texlurch]

Yeppers.

Plus, you are going to get some gas and crap in the chamber, regardless.

My CETME and G3 are NASTY!! LOL!!!

The gas system is the main issue in the AR guns, and the easiest to pick on by all the Mattel Toy Haters... :)

[97th Signalman]

In some ways, if the army hadnt jacked with the powders used and recomended for the rifle, the huge black eye that the rifle go in vietnam might have never happened, the fact they didnt issue cleaning kits with them was even worse. I guess there are teathing problems with new rifle systems, thus even the venerable garand rifle had changes from its first introduction but luckly there was more time before it had to become battle tested in WWII. I imagine if the orginal gas system had gone to war we would have had issues with that rifle too.(can you imagine the first time your rifle bumped into something in battle by muzzle and it failed to function due to problems with the orginal gas trap system vs the direct gas feed)
Good point Okie about the gas trap Garand. Even the Springfield 03 went through some revisions in the way of ammo, bayonet system, and metalurgy before it was acceptable. You could point to the Krag as a false start as a new smokless powder rifle since it was replaced in short order with a better military design. I also agree that MacNamara's whiz kids really screwed up the black rifle. The fact that its refinements were so successful that it's still around is testimony to the soundess of the design. That being said, I still think the AR would be more robust with a gas piston system just as the Springfield would be better with a mauser-style one-piece firing pin and no magazine cutoff.

[drhall762]

While I have yet to get my paws on one of the H&K Uppers I have talked with some guys that have tested and used them. They liked them and said the biggest thing they noticed was how much cooler the handguard/forend stayed after sustained firing.

They also told me the price tag was steep. Something on the order of $1200.00 per copy.

Don't know any of this for fact, just passing on what I've been told.

Dave :sniper:

[DAA1]

I read the article, sounds like a improvement on what we have now, but the army refuses to adopt it on the grounds that there is not enough of an improvement. I'll wager swapping out bolts and uppers for the newer piston design would not cost that much. Does not have to be an H&K upper, there are other folks who make them. Could be swapped out at the unit level with replacement uppers and bolts sent out and have the unit armorer do it.

I bet there would be an improvement over the current M16, and maybe we could see some improved qualification scores.

Like I have always said, if it makes sense, any sense what-so-ever, it aint gonna happen in the army.

I for one am going to add a ar with a gas piston to my want list.

[texlurch]

POF has them available a little cheaper than HK lists.

[nalioth]

<snip> I'll wager swapping out bolts and uppers for the newer piston design would not cost that much. Does not have to be an H&K upper, there are other folks who make them. Could be swapped out at the unit level with replacement uppers and bolts sent out and have the unit armorer do it.

<snip>

I for one am going to add a ar with a gas piston to my want list.

You mean like this (http://www.globaltactical.com/axami/shop.php?grd=377&prd=378)?

[DAA1]

Yep, but it won't ever happen no matter how much sense it makes. It is not a "new and improved", read that expensive as all heck and makes a ton of money for a defense contractor. So the army won't see it. SOC sees the H&K because they can go buy direct, see that part of the army is in a whole other universe. I think the govt ought to by the best weapons/rifles/personal defense equipment possible. Our soldiers deserve the VERY BEST, but congress and the red tape is a disgrace. At least the SOC soldiers who are out there stand a good chance of getting the stuff they need.

If I could add one value to the army values it would be "common sense", some things just make good sense, the piston upper makes "good" sense.

[Perro]

even in a full auto AK
you dont have a 10th of the burnt powder in the receiver area that you do in an AR - not even CLOSE

the most you have to worry about cleaning in an AK is the residue from the primer sealant, and thats about it - that crap gets all over the trigger parts

[Jacobite]

I still think my Cetme was the dirtiest system I ever shot. That rifle was a pig. Let those flutes get gummed up and watch Choppo start having issues also. Of course being Century put them together we can blame them instead of the design I guess. One thing I will never miss about my Cetme is cleaning it.

[97th Signalman]

I still think my Cetme was the dirtiest system I ever shot. That rifle was a pig. Let those flutes get gummed up and watch Choppo start having issues also. Of course being Century put them together we can blame them instead of the design I guess. One thing I will never miss about my Cetme is cleaning it.



I know what you mean. After a 100 rounds my CETME looks like the inside of a school bus's exhaust pipe. The difference in an AR is that you have to clean parts inside the bolt and at least with a CETME the filth is easier to get at. Of course then CETME's have those darn flutes that have to be cleaned. It doesn't bother me as much as it does some folks because I actually like cleaning my guns after using them.

[nalioth]

Of course then CETME's have those darn flutes that have to be cleaned. using a .45 bore brush or a .410 shotgun brush makes it an easy task, I don't see the hoopla about cleaning flutes.

[97th Signalman]

using a .45 bore brush or a .410 shotgun brush makes it an easy task, I don't see the hoopla about cleaning flutes.


Good point Nailoth. I probably spend more time getting the crud out of the locking recesses in the Trunion than I do messing with the flutes.

[Jacobite]

I still find my AR easier to clean than I did my Cetme. I think the FAL I built was the cleanest running except for my M1 Garands. I am a clean freak though. I clean all my rifles after every range trip even if I only shoot one mag out of them. I have tried to let the AR go for awhile just to see if that causes a malfunction but it is hard for me to walk past the safe knowing it is dirty.

[nalioth]

More eye candy for you guys who may have missed it. This is the segment from FutureWeapons that covers the H&K 416

Enjoy.

http://www.youtube.com/watch?v=5ObWpWXrt9I

[texlurch]

You mean like this (http://www.globaltactical.com/axami/shop.php?grd=377&prd=378)?

I have been looking at the ARE system for my next buildup; they are getting pretty good reviews..

http://www.aresdefense.com/GSR-35/GSR-001.jpg

[nalioth]

I have been looking at the ARE system for my next buildup; they are getting pretty good reviews..
Yup, good reviews, but best of luck finding any in stock. I hear they are backordered quite a ways.

If you do find any in stock, please let us know. :)

[gunnysmith]

There were some problems with the pin holding the gas cylinder to the gas block. I think they were foixing that but have had no reports.

[nalioth]

There were some problems with the pin holding the gas cylinder to the gas block. I think they were foixing that but have had no reports. I saw a review website and they said to use a solid pin, instead of the hollow roll pin the kit comes with. No problem after that.

[gunnysmith]

I saw a review website and they said to use a solid pin, instead of the hollow roll pin the kit comes with. No problem after that.

That's the part I couldn't find, There were some unhappy campers for a while though.

[Rampager]

One thing I usually don't see mentioned in AR debates is that the gas impingement system used in the AR was around for many years prior, being used in the Swedish Ljungman and Hakim quite successfully.

In the case of the Egyptian Hakim it used the gas impingement system along with an adjustable gas valve which made it quite reliable using various types of 8mm ammo. These guns operated in the desert in severe dusty environments quite reliably from what I’ve read and this was with milled receivers and pretty tight tolerances being of Swedish design.

My theory (and it’s just that) is that the gas impingement system in the case of the larger calibers like the Egyptian Hakim in 8mm mauser is that it had enough “umph” (power) to cycle the gun reliably under most any circumstance in semi auto form.

Where as in the case of the AR in .223, there just isn’t enough power there to get it to cycle when it gets a really hot and dirty. What I’m getting is, let’s say the AR was in .308 with an adjustable gas valve…would it cycle more reliably when dirty than a .223 version if dirty? Would a Cetme when dirty in .223 be as reliable as in .308? ...just wondering.

[nalioth]

One thing I usually don't see mentioned in AR debates is that the gas impingement system used in the AR was around for many years prior, being used in the Swedish Ljungman and Hakim quite successfully.

In the case of the Egyptian Hakim it used the gas impingement system along with an adjustable gas valve which made it quite reliable using various types of 8mm ammo. These guns operated in the desert in severe dusty environments quite reliably from what I’ve read and this was with milled receivers and pretty tight tolerances being of Swedish design.

My theory (and it’s just that) is that the gas impingement system in the case of the larger calibers like the Egyptian Hakim in 8mm mauser is that it had enough “umph” (power) to cycle the gun reliably under most any circumstance in semi auto form.

Where as in the case of the AR in .223, there just isn’t enough power there to get it to cycle when it gets a really hot and dirty. What I’m getting is, let’s say the AR was in .308 with an adjustable gas valve…would it cycle more reliably when dirty than a .223 version if dirty? Would a Cetme when dirty in .223 be as reliable as in .308? ...just wondering. FALs have adjustable gas valves. Most rifles with adjustable gas valves work better than those w/o. You just keep putting more gas into the system until the weapon is just too dirty to move. Hopefully sometime before you reach that point, you'll have a chance to clean it properly.

[gunnysmith]

One thing I usually don't see mentioned in AR debates is that the gas impingement system used in the AR was around for many years prior, being used in the Swedish Ljungman and Hakim quite successfully.

In the case of the Egyptian Hakim it used the gas impingement system along with an adjustable gas valve which made it quite reliable using various types of 8mm ammo. These guns operated in the desert in severe dusty environments quite reliably from what I’ve read and this was with milled receivers and pretty tight tolerances being of Swedish design.

My theory (and it’s just that) is that the gas impingement system in the case of the larger calibers like the Egyptian Hakim in 8mm mauser is that it had enough “umph” (power) to cycle the gun reliably under most any circumstance in semi auto form.

Where as in the case of the AR in .223, there just isn’t enough power there to get it to cycle when it gets a really hot and dirty. What I’m getting is, let’s say the AR was in .308 with an adjustable gas valve…would it cycle more reliably when dirty than a .223 version if dirty? Would a Cetme when dirty in .223 be as reliable as in .308? ...just wondering.

What you are saying is true, It's the gas pressure impulse duration time between a slower heavier bullet and a lighter faster one.
All based on the distance of the gas port from the end of the barrel.

[DaCapster]

I love all this crying.....Y'all should have got a woo!