Piston 4x to 8x > Direct Impingement.

 

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http://www.strategypage.com/htmw/htweap ... 91125.aspx

November 25, 2009: The U.S. Army has finally addressed years of complaints about the M-4 and M-16 assault rifles. The M-4 is a short barrel M-16, and has become very popular with the troops. The army has asked the Department of Defense for permission to spend a few hundred million dollars on upgrades for its 400,000 M-4 assault rifles. The big change is replacing the main portion of the rifle with a new component that contains a short stroke piston gas system (to reduce buildup of carbon inside the rifle) and a heavier (by five ounces) barrel (which reduces barrel failure from too much heat, which happens when several hundred rounds are fired within a few minutes.)

 

Much of this goes back to the decades old argument about replacing the recoil system in the M-16 assault rifles. This came to a head (again) two years ago, when the army ran more tests on its M-4 rifle, involving dust and reliability. Four weapons were tested. The M4, the XM8, SCAR (Special Operations Forces Combat Assault Rifle) and the H&K 416 (an M4 with the more dust resistant components of the XM8 installed).

 

The testing consisted of exposing the weapons to 25 hours of heavy dust conditions over two months. During that testing period, 6,000 rounds were fired from each of ten weapons of each type. The weapons with the fewest failures (usually jams) were rated highest. Thus the XM8 finished first, SCAR second, 416 third and M4 last. In response, the army said it was satisfied with the M4s performance, but was considering equipping it with a heavier barrel (to lessen overheating) and more effective magazines (27 percent of the M4s 882 jams were magazine related.) The army noted that the M4 fired over 98 percent of its rounds without problems. That missed the point that the other rifles had far fewer jams. In combat, each jam is a life threatening situation for the soldier in question. The army had been forced by Congress to conduct the tests. Congress was responding to complaints by the troops.

 

The XM8 had 127 jams, the SCAR 226 and the 416 had 233. Thus the M-4 had nearly eight times as many jams as the XM8, the rifle designed to replace it. The M4 had nearly four times the jams of the SCAR and 416, which were basically M4 type rifles with a different gas handling system. Any stoppage is potentially fatal for the soldier holding the rifle. Thus the disagreement between the army brass, and the troops who use the weapons in combat.

 

In dusty places like Iraq and Afghanistan, you have to clean your M16 and M4 rifles constantly, otherwise the combination of carbon (from the recoil system) and dust in the chamber will cause jams. The army and marines both decided to stick with their current weapons, rather than adopt an easier to maintain weapon, like the XM8 or H&K 416, because of the billion or so dollars it would cost to switch rifles.

 

If the issue were put to a vote, the troops would vote for a rifle using a short-stroke system (like the XM8, SCAR or H&K 416). But the military is not a democracy, so the troops spend a lot of time cleaning their weapons, and hoping for the best. The debate involves two intertwined attitudes among senior army commanders. First, they don't want the hassle, and possible embarrassment, of switching to a new rifle. Second, they are anticipating a breakthrough in weapons technology that will make a possible a much improved infantry weapon. This is likely to happen later, rather than sooner, but the generals kept obsessing over it.

 

Earlier efforts to just get the troops a more reliable rifle have failed. Back in 2005, the U.S. Army's design for a new assault rifle, the XM8, was cancelled. But now the manufacturer has incorporated one of the key components of the XM8, into M4 rifles, and calls the hybrid the H&K 416. Heckler & Koch (H&K) designed the XM8, which was based on an earlier H&K rifle, the G36. SOCOM is using the 416, but no one else is (except for a few police departments).

 

The XM8 (like the G36 and 416) uses a short-stroke piston system. The M16s uses the gas-tube system, which results in carbon being blown back into the chamber. That leads to carbon build up, which results in jams (rounds getting stuck in the chamber, and the weapon unable to fire.). The short-stroke system also does not expose parts of the rifle to extremely hot gases (which wears out components more quickly). As a result, rifles using the short-stroke system, rather than the gas-tube, are more reliable, easier to maintain and last longer.

 

H&K developed the 416, for SOCOM, at the same time the XM8 was being evaluated by the army. SOCOM got the first 416s in 2004, a year before the army cancelled the XM8. The 416 looks like the M4, for the only thing that has changed is the gas system that automatically extracts the cartridge after the bullet has been fired, and loads the next round. SOCOM can buy pretty much whatever they want, the U.S. Army cannot. SOCOM listens to what its troops want, the army often doesn't.

 

The army is also making three other changes, as part of the M-4 component replacement. There will be improved trigger pull characteristics, a stronger (less likely to fail) rail on the top of the rifle (for fitting scopes and other accessories), ambidextrous controls (to make life easier for lefties) and a round counter (in the pistol grip) to track the number of bullets fired over the lifetime of the rifle (makes for better data on how rifles perform over time, and for scheduling the replacement of components.)

So it seems to be a complete new upper for the M4? IANAARG, so I dunno about such things,except the M16 from when I was in, and teh discussins here.

A 6.8 M4 would be awesome!!!

A 6.8 M4 would be awesome!!!

 

A change in ammunition is the least likely one to happen. Too much in terms of logistic and stockpile issues... then there are our NATO STANAG arrangements.

I say let SOCOM field test all available options. Eventually when SOCOM comes to a consensus, maybe their brass can start pushing for a wide spread change. Not like the Army ever listens to their enlisted folk, ever, so, it wouldn't matter if a petition signed by every enlisted person was presented. But who knows?

The AW unit stopped using the HK 416, so I doubt that rifle will get picked up for the long haul. I think the SCAR has the best chance right now because of the wide spread field test it is receiving with the Ranger battalions in current operations (similar to when SOCOM and other mission-specific units [like 10th MTN] were field testing ACUs before they were adopted).

"Be, all you can be", but without a reliable rifle! :roll:

I say let SOCOM field test all available options. Eventually when SOCOM comes to a consensus, maybe their brass can start pushing for a wide spread change. Not like the Army ever listens to their enlisted folk, ever, so, it wouldn't matter if a petition signed by every enlisted person was presented. But who knows?

The AW unit stopped using the HK 416, so I doubt that rifle will get picked up for the long haul. I think the SCAR has the best chance right now because of the wide spread field test it is receiving with the Ranger battalions in current operations (similar to when SOCOM and other mission-specific units [like 10th MTN] were field testing ACUs before they were adopted).

 

The ACR is going to be where it's at. American Designed, American Made. From what I understand taking the best from the best. So far though, it was never in any of the competitions, so it's a long ways off.

I'm hoping big Army does choose the ACR. Though I've never had the chance to handle one, it does seem like a far better package. With that said though, the SCAR is in one of the last phases of field testing. That and the fact that the Army does have contracts with non-American companies (M9 by Beretta, M249 by FNH), I wouldn't be surprised if the contract for a new battle rifle also went foreign. With that said, I believe the SCAR is still manufactured here in the US exclusively, even though its owned by FNH.

All I need is an E-tool.

Hate to say this, but if they went to a midlength gas system and medium to heavy barrel contour, this would probably eliminate the majority of reliability problems.

 

But....

 

Count me in as an ACR fan!!!

Buying ACRs and SCARs would be far too expensive for a slight change in performance. I can understand giving SOCOM and Rangers specialty weapons like the SCAR, but to give every transpo, intel guy, and infantryman a SCAR would cost far too much.

 

The Army should have a contract worth a few hundred million to make short-stroke piston uppers for the existing M4/M16 stocks. This solves multiple issues:

 

(1. Retain the M4 lower receivers and retain a similar weapon system. This minimizes any possible retraining. With an entire new weapon system like the ACR, you'd need to train troops extensively on a new weapon. When you replace the upper, the troops are still familiar with all the lower-receiver configuration. And to be honest, the M4 has a great lower. I shoot lefty and I never had a problem handling the M4 in my time.

 

(2. A lot lower cost than a new system. Again, you're retaining all the lowers, so things should work fairly well.

 

(3. A short-stroke system runs a lot cooler than a gas impingement system. Overheating is a huge issue and since pistons don't dump gas right into the chamber like a direct-gas system, this would allow the weapon to run a lot cooler. Another is the issue of carbon buildup. A piston-system doesn't dump residue in the chamber like impingement does, making the weapon a lot cleaner after many shots. While any soldier worth his salt should be cleaning his weapon regularly, it would make for less dirty, and consequently, more reliable weapon.

 

 

Basically, a short-stroke piston upper would solve a lot of the M4s problems, while being a lower cost than other alternatives and retaining the familiarity of the lower receiver. The Army could also invest in quality magazines for infantry-types (infantry, cav scouts, combat engineers, MPs, etc.) to reduce combat stoppages, and let the non-combat MOSs use the leftover STANAG magazines.

 

I say that the Army should have a contract for the uppers rather than just using H&K 416 system, because while H&K makes good stuff, its typically overpriced for what it does. I trust FN, Colt, and others could come up with a well-made and functioning short-stroke system for the M4 that can compete with an H&K design.