DI or Piston?

[Arctic1]

I have explained time and time again the fouling characteristics of the weapon. I have described in detail where the fouling ends up.

You stated first that the carbon is deposited in the gas block and the piston face, and claim that this is the same amount that goes back into the carrier on a DI gun.
Then you circle back and say you never claimed that it was excessive fouling.

I showed you a picture of the HK piston, how it looks after extended use.
Other users have shown you pictures of their BCG after 500 rounds, and there is NO fouling on it.
I linked to a thread that shows the temp differences in several areas on piston and DI guns after rapid fire of 112 rounds (4 mags of 28 rounds):
https://www.m4carbine.net/showthread...-detailed-look

I have loads of experience with regular DI guns, and the two do not compare at when it comes to the amount of carbon deposited ANYWHERE in the gun. At all.

[MistWolf]

I think you should go back, read what I wrote and parse it carefully

[Arctic1]

I think you should go back, read what I wrote and parse it carefully

This is from your first post in this thread, post #12:

When the piston is in the gas block, the piston is a smaller diameter and is subject to more heat and at least as much fouling as a piston in the carrier. The advantage to having the piston in the carrier is that it can be lubed which helps to keep the fouling soft and easier to clean and the gas has cooled significantly passing through the gas tube.

I don't have any experience with ARs with gas block pistons but I do with FALs which is similar. I find a conventional AR easier to clean and maintain.

Then, in post #68 you say the following:

I'm not claiming the deposits will be excessive because they won't be.

Maybe you are a visual learner, so here is what will never happen with a piston gun, ever. Nowhere in the gun will there be this much gunk:



Also, as far as temps go, here are measurments done using thermal imaging:



These are the reasons a piston gun is said to run cooler and cleaner.

[MistWolf]

Let's take a look at the following

When the piston is in the gas block, the piston is a smaller diameter and is subject to more heat and at least as much fouling as a piston in the carrier. The advantage to having the piston in the carrier is that it can be lubed which helps to keep the fouling soft and easier to clean and the gas has cooled significantly passing through the gas tube

"Subject to" means "Exposed to". It means the piston has to deal with at least as much fouling when it's in the gas block as it does when it's in the carrier. The gas carries particulates. The particulates are what I'm talking about when a talk about fouling. As the gas travels along it's merry way, it leaves deposits of fouling behind, especially when the gas needs to change directions and when the gas cools.

About the gasses cooling in the gas tube. It happens. It's science. If the gas tube doesn't absorb heat from the gas, how does the gas tube get hot? Heat transfers from the gas to the tube then radiates from the tube to surrounding air. That means the gas carries less heat as it enters the expansion chamber of the carrier compared to when it enters the gas block.

This is the complete paragraph from post 68

Surely, you aren't going to tell me the face of the piston will collect no carbon deposits. I'm not claiming the deposits will be excessive because they won't be. (The face of the piston is what you call the tip)

The only way that the deposits from the gas block have no bearing on ease of cleaning, is if those deposits are never cleaned. This is not the same thing as me claiming these deposits must be cleaned to keep the weapon functioning, because I'm not

I was explaining that while the gas block piston is subject to (exposed to) fouling, the build up of deposits isn't excessive.

There is more to the story of the carrier in your photo than it's dirty. Clearly it was subject to more than normal firing schedule before being cleaned.

I know when you say a "a piston gun" you really mean an HK AR. But if you never clean and lube a gas block piston rifle, there will be a nasty buildup. The following photos are of a FAL that fired 16,000 rounds without maintenance. It's not an HK, I know. Do you have photos of an HK AR that has fired 16,000 rounds without maintenance? Not being snarky, I'm interested to see them.







I never claimed that the carrier of a standard AR doesn't get hot or that it will be as cool as the carrier of a gas block piston AR. A claim like that would simply be ridiculous.

I'm simply examining the science. After this, if you still think I'm disparaging your beloved HK, or of you want to look for flaws in my words instead of discussing the science, you're on your own

[Joe Mamma]

I can only suggest that you seek out the opportunity to educate yourself by trying one.

I have found that the vast majority of people who dislike piston ARs are people who have never used one or never fired more than a few shots from one. Everyone is entitled to their opinion of course. But it's an interesting observation.

Joe Mamma

[Arctic1]

But if you never clean and lube a gas block piston rifle, there will be a nasty buildup.

No, there will not be.

I don't have pictures now, but I will continue shooting my gun without cleaning it and break it down at about 3000 rounds and see how it looks.
I don't shoot very much rifle these days, preparing for the handgun World Shoot in France, so I'm only at approx 800 rounds since my last clean and lube.

As to your point on the gas tube heating up and slightly cooling the gas, sure. From the gas block to the carrier key you lose about 200 or so degrees on the DI gun, compared to 370 on the piston gun. The DI bolt body is 100 degrees hotter than that of the SCAR or the piston AR. The carrier key is 160 degrees hotter. The firing pin and cam pin are 120 and 90 degrees hotter, respectively. That is a significant difference.

As I said above, the lack of fouling in the upper/lower and the cooler temps of the BCG components is why people say piston guns run cooler and cleaner. You can argue semantics all day long, but you could see for yourself if you would just try to shoot one.

[Arctic1]

I have found that the vast majority of people who dislike piston ARs are people who have never used one or never fired more than a few shots from one. Everyone is entitled to their opinion of course. But it's an interesting observation.

Joe Mamma

Exactly.

[Arctic1]

There is more to the story of the carrier in your photo than it's dirty. Clearly it was subject to more than normal firing schedule before being cleaned.

According to the thread here on the forum, it had seen 3500 rounds of 5.56 and about 5k of .22LR (most of the .22LR are suppressed)

Thread is here:
https://www.m4carbine.net/showthread...te-pg-2)/page4

[26 Inf]

FWIW, I'm wedded to the DI, I have six in the safe, I own no piston AR's.

With that out of the way, I have a question: In the much maligned 'Individual Carbine Competition' was 'Rifle C' a DI or piston design?

A competing rifle outperformed the Army’s favored M4A1 carbine in key firings during a competition last year before the service abruptly called off the tests and stuck with its gun, according to a new confidential report.

At the time, the Army explained the cancellation by saying none of the eight showed a huge improvement over the M4. In the past, the Army, with an inventory of 500,000 M4s, has defended the carbine as reliable, accurate and popular among the large majority of soldiers. It has been upgraded throughout the war on terror to improve its magazine, barrel and sights.

The Center for Naval Analyses (CNA) report shows that one competing gun outperformed all other competitors, including the M4, on some key tests. The results show there was a potentially better gun for soldiers.

“It was misleading for the Army to say none of the weapons passed the test,” said a U.S. official critical of how the Army buys small arms. “It was true, but it was extremely misleading. They set the requirements for the mean round between failure at around 3,000 rounds. That’s extremely high.”

He added: “You had one weapon beat the pants off your incumbent, and the result of this was not to do more testing. You had the opportunity to keep working and pursuing a better weapon, and you chose not to.”

The CNA report does not name the eight guns and producers, apparently to protect proprietary information.

The U.S. official knowledgeable about the report said gun “A” was the Army’s M4A1, an enhanced model of the basic M4.

The CNA report contains three significant graphics.

In one, reliability was measured against the M4 as the baseline. Gun “C” scored 25 percent more reliable than the M4A1 and better than all others.

A second graphic shows test results for “mean rounds between failures.” This is perhaps the most important test because it shows how many shots the rifle can fire before stoppage.

Again gun “C” was by far the best, achieving more than 2,500 rounds. The M4A1 failed after 500 — a gap that can make a significant difference in battle.

This test was a measurement of Class 1 and Class 2 magazine stoppages, in which one soldier can clear the gun himself within 10 seconds or more than 10 seconds, respectively. The U.S. official said classes 1 and 2 are the most common stoppages in battle.

A third graphic shows the M4A1 performed best for Class 3 stoppages, which are more significant failures that require a specialist, or armorer, to clear.

It achieved 6,000 mean rounds between failure. Gun “C” achieved about 4,500 rounds.

http://www.washingtontimes.com/news/...le-outperform/

I know this has been hashed and rehashed, unfair dust tests, yada yada yada.....

Bottom line is apparently one rifle did substantially better, which one was it?

[Arctic1]

Bottom line is apparently one rifle did substantially better, which one was it?

I have heard it claimed that it was either the FN submission or the HK submission, both are pistons.

However, this is completely unsubstantiated info.