Weapons: Heat Impaired Accuracy


June 26, 2014: The German army is again dealing with complaints that its standard assault rifle, the G36, suffers accuracy problem at long range (over 200 meters) when the barrel gets very hot. It’s an old problem that didn’t show up until the G36 was used a lot in combat during hot weather in Afghanistan. The problem appears to be the polymer (plastic) parts of the rifle get a bit soft when the metal parts get very hot due to heavy use in a short period of time. The barrel and receiver can move a tiny bit under those conditions and that throws off accuracy to a small degree that becomes noticeable only at longer ranges. No one has come up with a practical (workable and affordable) solution. The German government insists the problem has to do with bad ammunition but the ammo manufacturers deny that. In response to all these conflicting ideas the government has ordered yet another investigation and a temporary halt in purchases of G36s.

The G36 has been the German infantry assault rifle since 1997. It was very popular initially, especially since it used a short-stroke piston system. The M16s uses 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.

Meanwhile heat has long been a problem for infantry weapons, especially those capable of automatic fire. The mass media is prone to misinterpreting these effects. For example the mass media is fond of talking about American assault rifles overheating and jamming. Some of the reports displayed a remarkable ignorance of how military rifles operate. A typical bit of misinformation reported rifle barrels white hot with heat. That's a physical impossibility, because of the metal used for these rifles. Long before the rifle barrels turned any color from heat, rounds would automatically fire ("cook off") from the heat, and the barrels would fail (split apart). The reporters also seemed unaware of how automatic weapons handle heat. Assault rifles are built to fire about once every four seconds for hours, without any heat problems. Machine-guns do have heat problems, and are designed with easily removable barrels, so you can switch in a fresh barrel. In short, any automatic weapon will overheat if you put too many rounds through it in too short a time.

German troops are taught all about this heat problem, and are reminded that they must either cope with it, or risk death. The G36 problem is what engineers consider “acceptable” given the design. It is always possible, especially in a desperate combat situation, to use weapons in ways they were not designed for.  Well trained troops are taught the consequences of certain extreme situations, so that at least they know what to expect.

In the U.S. military assault rifle problems tend to be about rifles jamming (and not because of heat problems). This goes back to the decades old argument about replacing the recoil system in American assault rifles. This came to a head (again) in 2007, 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. 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 systems. 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 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 keep 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).

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. In trying to avoid embarrassment and scandal, the army leadership is blundering into it anyway. Now the issue is getting revived, and is getting more attention from Congress. The army doesn't like that either.




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