Paper Tiger Killers, The M18 Hellcat 76mm GMC - TANKS

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Carl the near dead #1 · Sep 13th, 2017 · 2 · ·

In order for a tank to be considered a paper tiger first it must be considered a good tank. Unfortunately America and Great Britain really didn’t make any tanks during the course of world war two that are rated by culture to be good. Most of the tanks that do have a good reputation were german, and whether this is earned or not is a different discussion. A few Soviet tanks reached this distinction but as far as the western Allies are concerned there are precious few tanks that can even be considered good enough to be in danger of being paper tigers. Due to the dismal state of British tank design they are realistically only two, maybe three tanks from the United Kingdom that have a good reputation at all. And one of them is a Sherman (which will be covered).

From the American side of things with the Sherman having been effectively defamed over the course of years and the Sherman being the main tank of the American forces there are few other contenders for a good American tank. As far as the popular understanding goes the best American tank of world war two was the M26 Pershing, riding a mixture of good performance, combat against a defeated military, and a few flat out myths to a good reputation. And its day in the series will come.However there is another American armored vehicle that has fairly recently gotten a very good reputation. This would be the M18 Hellcat.

The Hellcat has at least to my knowledge enjoyed a resurgence in popularity thanks to video games like World of Tanks and War Thunder. It’s good performance in these games usually leads people to do a little more research, in the first thing that they will often read is a very vague statement about how the M18 had the highest kill to loss ratio of any American armored vehicle in WWII. And with some real positive data to back up in game performance the M18 looks to be one of the few American vehicles of the period that most can look back fondly on. Indeed, the M18 is a popular tank (destroyer).

It has shown up in numerous videos on youtube, several car publications, a episode of tank overhaul (which had more than a few glaring falsehoods), and a direct to video movie, all within the past 15 or so years. If any evidence was needed to prove that the tank is popular, on only needs to look for the technical manuals. The technical manuals detail all the minutia and operations of the vehicles, and for most American vehicles the TM’s are available free on the internet for download. The M10 TM's are find-able HERE, for example. But the M18’s is harder to get. Not harder to find though. It’s HERE. For 20 dollars. In 2013 the War Department determined that they could make money off of the technical manual of this TD and not the others, and that’s pretty telling.

So with a good reputation there is the risk that reputation is overblown, and that this is a paper tiger. But before we can discuss that we must first understand the development of the tank, and in this case that takes some explaining. Because that requires knowing about the Tank Destroyer Battalions and why it existed.

After the fall of France in 1940 within a month, with 2 of the most powerful armies in existence being soundly defeated by the German blitzkrieg, every country in the world that had a chance of having to fight Germany had to develop a counter to massed coordinated panzer attacks. As the US Army saw it, the problem was one of defenses. Static defensive positions like the Maginot line could be easily bypassed, and were incredibly time consuming and expensive to build in the first place. So for more temporary defensive lines, the problem was this. There was no way to have a concentration of anti-tank guns for the whole length of the front that could stop a concentrated push of tanks on a small area. If the anti tank guns were massed in one point to be able to resist this concentrated push, it would simply bypass this mass. In essence, they believed that no defensive line on a front would be able to resist a panzer attack. The panzers would always get through.

So the counter was the tank destroyer corps. Held in reserve, a concentration of sufficiently mobile and powerful antitank guns would be activated upon the enemy’s attack, and would move to counter attack the massed panzers in its own mass of concentrated firepower. In this way the enemy would be stopped after the initial breakthrough.

Now, and this is important to the M18, the two men in charge had different ideas on what was most important to the tank destroyer corps. Lt Col Andrew Bruce believed that the statement should read sufficiently MOBILE and powerful, with the tank destroyers being useless if they could not react to a breakthrough quickly. Brigadier General Leslie McNair thought that the statement should read Sufficently POWERFUL and mobile, because what good was a fast tank destroyer if could not take on armor easily. To McNair, the Ideal TD was a 3 inch anti-tank gun towed by a deuce and a half. It would be able to be towed into a good ambush spot, easily concealed, and at the time of the idea able to destroy just about any tank in the world from the front.

But Lt Col Bruces ideal TD, that was much different. It would be a self-propelled gun, with the maximum of engine and automotive power and the minimum of armor, and a gun good enough to get the job done. What he wanted would become the M18. So how was it developed?

Well, very weirdly was the answer. You see, nearly every armored vehicle that the United States designed during the war was designed by the Army Ordinance department. But there are a few exceptions, one being the M22 Locust airborne tank, and the main one being our M18. Initially, the requirement for the new TD went to the Marmon-Herrington Company that was working on the M22 to build a 37 mm Gun Motor Carriage (GMC) based on that design. This was in late 1941. Now whether this work was assigned outside of the Ordinance Department simply because they didn’t have the designers to spare or because Lt Col Bruce had to circumvent the Ordinance Department to get his ideal TD I do not know. Regardless, quickly there were misgivings about Marmon Herrington’s ability to deliver the goods, so the project was transferred to Buick of the General Motors Company.

And from here, the requirements changed. The 37mm gun was determined to be obsolete, so the requirements moved to the British 6 pounder to make the T49 GMC. When that was going through testing, the gun was changed to the 75mm of the Sherman, and the turret changed to compensate by being open topped. This became the T67 GMC. In late 1942, the gun was changed a final time to the 76mm cannon. With the gun determined to be sufficient, the vehicle was redesigned by Buick to improve the hull, engine, and turret. This would be the T70 GMC. After some testing, this would be accepted into service in July of 1943 as the M18 Hellcat.

As a final note before we finally start talking about the vehicle, it wears its civilian origins with Buick proudly, which makes for some strange touches that are not present with other vehicles. One of which is the name and the PR that it got. You see, until November of 1944, American tanks did not have names. A GI would not say “look, here come the Sherman’s!” he would say “Look, here come the mediums!” or “Here come the tanks!” or “Here come the M4’s.” The only AVF that did have a name before November of 1944 was the M18, because Buick called it the Hellcat, and it stuck. The Tank Destroyer Corps emblem became the one made by Buick for the M18, and it shows. And the Sherman may have been made by Ford and General Motors and Fisher Automotive and the Lima locomotive works, but the Hellcat was made by Buick. And no one really knows who designed the Sherman, but the Hellcat was definitely designed by Buicks chief engineer Harley Earl. In a way, the press surrounding the M18 back in the day may have an effect on how it is perceived now.

And with that out of the way, we can now look at the M18 Hellcat as it was. Starting with the armor.

Armor:

This will be by far the easiest section that I may ever have to write, because the M18 Hellcat doesn’t have any. The hull is uniformly half an inch thick all around, except for the turret front where it’s a whopping 1 inch thick. And with a gun shield that’s ¾ of an inch thick it has a maximum armor of a whopping 1 ¾ inches! And it has no turret roof.

On the one hand, this is exactly as bad as it seems. Forgetting about the raw thickness for a second and focusing solely on the turret roof hole, the M18 is very vulnerable to air bursting artillery, small arms fire from high angles, and air attack. And while air attack really was never the threat the other two were, and one would have to think that this vulnerability would make an M18 commander cautious about going into urban areas.

But on the other hand, the thickness of armor in some cases really doesn’t matter. If a M18 were fighting Panthers for example, it would be on the same playing field as a Sherman, because both are going to be penetrated by any rounds from that gun. It is in only a few cases where this would work (a Sherman would be nearly invulnerable to obsolete 37 and 50mm antitank guns, which would both ruin a M18) but such cases did exist.

But who am I kidding? The M18 had the worst armor for the time of any fighting vehicle of the war.

Armament:

Perhaps one of the reasons that I chose to cover the M18 is because it would be easy due to the retreading of familiar equipment. Because the M18 shares the same cannon with the 76mm shermans (but without the stabilizer), it’s really nothing new. Against most German armor, it’s deadly. Against Tigers it was deadly at nearly any range with the M93 HVAP round, and was able to defeat it under ideal circumstances with the regular M62 round. Against Panthers it was ineffective at any range with any round against the front, but effective at any range with the standard round with a flanking shot. And against King Tigers it was effective at most ranges against perfect side on shots.

The two main advantages the M18 had over the Sherman in terms of gun performance against enemy tanks were the fact that it had priority on HVAP rounds, which gave it better chances against heavily armored tanks (again, not terribly much, but better), and the fact that its role was more defensive. The M18 would react to an armor attack by moving into a good ambush positon and waiting, and in these cases it would have the deck stacked in its favor. Yes, its gun is only effective against the Panthers and King Tigers sides, but you could about guarantee that any shots the Hellcats would set themselves up for would be on the Panthers and King Tigers sides. In this way the 76mm gun fit Lt Col Bruce’s vision of a powerful enough gun.

Apart from its anti-armor capabilities the M18 along with its TD brethren was commonly used as an artillery piece, and was outfitted as such with an azimuth indicator and indirect fire tables for this role. As mentioned in the 76mm Sherman article it was actually quite good at it, with a fragmentation effect to rival the 105mm howitzer while doing less physical damage it was ideal for bombarding important infrastructure without blowing it to smithereens. Also, its high muzzle velocity and flat arc took away the warning of bombardment that the relatively slow and high angled howitzers gave the enemy. Often when 105’s fired, the gun was heard before the round arrived, but not with the 76mm cannon. This gave it added psychological effect in this role.

In all, the 76mm cannon fit the Hellcat well, giving it the ability to defeat all German armor in its role and also function in other purposes.

The M18 also has a .50 caliber machinegun on a ring mount for the commander. It’s good for light AA, but on a TD that’s really it.

Mobility:

Yes, it’s the one that you all have been waiting for, the Hellcats legendary mobility. You all want to know if it is as good as it’s been made out to be, and I am happy to report that the answer is yes.

With some caveats.

First, the basics and the statistics. The M18 had a ground pressure of 11.9 PSI at full load, better than the Sherman’s exempting the E8 and the Panther tank as well. This was with the original 14 inch wide tracks, but the final run of Hellcats in late 1944 (450 or less) had wider 21 inch tracks, giving it a fantastic ground pressure of 8.17 PSI. The tank at full load weighed 40,000 pounds, or 19.5 tons, and with the Wright Continental R-975 C1 engine producing 340 net HP (or 400 Gross), the power to weight ratio was 17.5 HP per ton, which is pretty good. However this was changed starting with the 1350^th tank to the R-975 C4 which had an HP of 400 net (460 Gross), and gave it a HP per ton of 20.5. I don’t have to tell you that’s a really good figure. The tank can’t neutral steer, but for its role that’s a minor point.

So, it has good flotation, which seems to point to good off road mobility, it has very high power to weight ratios, it has a high top speed of 50 MPH on road, and it has that newfangled torsion bar suspension that looks pretty promising and gives a good ride. So what’s the catch?

As always, if you want an unbiased opinion on something give it to a friend. As usual because the documents are readily accessible and already translated for me, that friend will be the Soviet Union, testing a T70 GMC. So how did it do?

On roads it never quite got to 50 Mph, only achieving 47 mph in one run. It would reach 70kph (43 MPH) after a minute of acceleration on smooth roads. If it tried to break while going at speed it would skid, as one would suspect. Initially, the only remark against it was high fuel consumption, 200 liters per 100 kilometers on road (nearly a gallon a mile).

On dirt, it actually went kind of slow. They pegged it at 24 kph on average. By comparison the M3 Stuart averaged 29 kph. It could only drive in second gear, as the third gear didn’t have enough torque to power through snow and other such things. And fuel consumption was now 357 liters per 100 km (up to 1.5 gallons per mile)

Driving off-road in snow was pretty bad. It could only drive in first gear, averaging 20 Kph, which just isn’t fast. And now it was at 708 liters per 100 km (3 gallons per mile). It could only drive up a 16 degree slope before the traction and the low torque took hold and stopped it.

In all, they concluded that the tank had two chief flaws in mobility. The engine constantly worked at high RPM’s for the maximum horsepower, and therefore guzzled fuel like no one’s business, and the torque converter fitted to the tank simply didn’t put down enough torque for it to be mobile anywhere but on paved roads. It was a pretty crushing verdict.

However, there’s more to the story, more that I don’t have vision on. See, the Soviets documented which M18 they got, serial number 40108549. Looking at the batches of M18’s this was the 445^th vehicle made, and it turns out that this is very important, because the United States had similar issues with the tank failing to climb slopes due to their torque converters, and all tanks from number 684 onwards had modifications that fixed this. The first 684 were returned to the factory, 10 converted to T41 prototypes, and 640 being changed to M39 Armored Utility vehicles. This left 34 in their original form, and one of them was the one sent to the Russians. So their thoughts on that vehicle were correct, but they were also not representative of the majority of the production, and not representative of any of the vehicles that fought in Europe. So the question is now how much the changes made improved the off-road capabilities?

There is data collaborated in several documents, that the improved Hellcat could climb slopes of 31 degrees. This seems to indicate that the torque converter was effectively fixed. If so, it would have also improved the vehicles general off road performance, and if that were improved then the M18 may well have deserved its title of the most mobile vehicle of the war. Unless I can find confirmation (a trials report would be ideal) on this I must look at the M18 skeptically, as a vehicle that was only really mobile on highways.

Now is that a fault? Not in Western Europe, which had a very good road system to operate on, but in some circumstances it could have been.

In conclusion, the mobility of the M18 was at a minimum good, and potentially great.

Reliability:

Again, a short segment. We already know that the engine is reliable, because it’s one of the engines on the Sherman. And the Russians in their report dedicate only 1 of their 40 conclusions to reliability and it reads verbatim “The vehicle is reliable. No components or mechanisms of the vehicle broke during trials.”

So it’s reliable. Yay.

Repairability.

Again, a short segment. The M18 was easy to repair. The engine deck and the rear of the tank could open quickly for access to the engine, which could slide out of the tank via little rails on the rear door for easier access. The transmission and other assemblies could do a similar thing via a removable cover at the front. In theory the torsion bar suspension was easy to change, but if one got bent this would become a nightmare. But that was honestly the hardest thing to repair. Like the Sherman, it gets high marks here.

Ergonomics.

Ergonomically, the M18 seems to be a mixed bag. There are a few things that simply don’t really make sense, and nothing is going to illustrate this more than the assistant drivers position.

For the life of me, I have no clue what the F*** this guy is supposed to do. On a Sherman, he’d be manning the bow machine gun. But there is no bow machine gun. On a M10, he’d be a radio operater. But there is no radio. He is literally an assistant driver, which means that very often he isn’t even driving the tank. he has no gauges to determine what he is doing, but does have all the controls needed to drive. And I have no clue why he is there. I especially have no clue why he is there when the army recommended that the crew be reduced to 4 for the preceding tank, the T49-T67. One would think that A, that recommendation would be followed seeing as how the assistant drivers job is Ill defined and B, that the space taken up by the assistant driver could be used for greater ammunition storage. But it’s really neither of the two. I don’t get it.

So the driver then. He steers via steering levers, which is pretty standard. What isn’t pretty standard is the gearbox. It’s an automatic. Sincerely. It has 3 positions labeled for the speed that the tank can go at each, and one reverse gear, and apart from that the tank takes care of it. he has the needed gauges on his left, and that’s about it. there’s really only one ding to be had about this, and that is concerning the hatch design.

It’s downright bad. It’s a two piece split hatch, that splits with one half being about twice as large as the other. So when you open the hatch you have to open up two pieces instead of one, and one of those will weigh twice as much as the other. The larger piece has the rotating periscope that serves as the one and only means of seeing out when buttoned up, but because of how the hatch is directly over the driver and how it’s split at the 2/3’s mark and the periscope is directly overtop of the larger part the driver has to lean to the left constantly in order to use it. It isn’t right in front of him, and it’s just confusing and needlessly uncomfortable. Doubly so when you look at the T67 and you see a one piece hatch that has the periscope line up properly. The hatch makes no sense.

So let’s go to the loaders position. He sits on the right hand side of the gun, which is rotated at 45 degrees so the breech is easier to operate. He has 9 ready rounds in front of him, along with 6 cans of .50 cal ammunition. There are two main problems with this situation. One is the relative lack of ready rounds. Yes, 9 rounds capacity is better than many tanks, especially if there is one in the breech giving it 10 rounds on tap. But when this tank destroyer expects to fight concentrated pushes of armor I have to wonder why the .50 cal boxes aren’t moved somewhere else to make room for more ready ammunition. The back of the turret looks fairly open for the .50 cal boxes to be put by the radio, which would also make it easier for the commander who’s shooting the machine gun to access. Most likely it’s a matter of balancing the turret, but if it isn’t that then I really have to wonder about the layout of ammunition.

The other issue is the fact that the loader must do all of his work while sitting down. This is weird and uncomfortable and restricts his movement and therefore the tanks rate of fire. The Russians took note of this, pegging the maximum aimed rate of fire at nearly 10 rounds per minute. This isn’t bad, but the Russians were sure it could be better.

The gunner’s position is actually really good though. Like with the Sherman, he has a periscope for laying the gun on target, and a telescope for precision fire. He has an automatic traverse that can turn 90 degrees in less than 4 seconds, and a manual for precision aiming. Not much else to say about this. To the commander.

The commander’s positon is a mixed bag. On the one hand, he has the greatest visibility of any TC ever, and therefore the most situational awareness. The radio is right behind him and easy to reach. There are some issues however. First is the lack of a fold away seat that allows him to see out of the turret while sitting. If he is looking out of the tank (and, you know, doing his job) he is standing. Dang, that has to get uncomfortable. And second is the .50 cal in the ring mount. It is constantly in his way, and there doesn’t seem to be a really good way to move it out of the way when he isn’t using it (which is, you know, 95 percent of the time). In all, it has it’s pros and cons. And that’s a good summary of the tanks ergonomics.

As a final thought, there has to be something said about the tanks comfort in winter. As an open topped TD it is obviously going to suck, and because the engine draws air from the crew compartment it makes there be airflow and that makes it even worse. But from 1700 onward there were blowers installed that blew hot air into the crew compartment when the engine was on. Sooo, maybe you would have lucked out if you were a Hellcat crewman.

Production.

Production was 2507 vehicles in total. Of these, 684 were never used (these being the ones with the original transmission before improvements.) of the ones left, there were a total of 217 AFVs lost to all causes. In all this isn’t fantastic, but there were more Hellcats made than Tigers, so that has to count for something.

And this will start to bleed into the conclusions, but the intent wasn’t to make only 2500 Hellcats. Originally, the plan was to make 9000, with 1600 for lend lease. And this didn’t happen. And it didn’t happen because it sort of wasn’t wanted. As said before, the Soviets rejected it, and it seems that the British arrived at the same conclusion (although if I ever go to Bovington I’ll have to take the time to look and see if they have the trials results for their 2 T70’s). The M10 crews usually didn’t really want it. A report of the new weapons board even in April of 1944 stated that the M10 crews were happy with what they had, and wanted the upcoming T71 (M36) 90mm GMC instead of the M10. There would have been more, but people just didn’t really want them as much as Buick had hoped.

Conclusions.

First of all, I think that the M18, despite its shortcomings, is fundamentally a good vehicle. For the role that it was intended to be in it did its job very well, taking out 526 German armored vehicles for 217 total losses. On the face of it, that’s a kill ratio of 2.42 in favor of the Hellcat. And when you consider that the 217 hellcats lost were lost to not just enemy tanks, but enemy mines, anti-tank guns, artillery, and the occasional breakdown, that kill ratio just gets better.

But it could have been better. There are a few points in the ergonomics section that really could have been improved easily to make the tank a bit more effective. And then one has to wonder about other, marginally harder improvements. Things like a thin roof for shrapnel could have gone a long way.

And further than that, one has to wonder the following questions. What does the M18 offer over the M10, and what does the M18 offer over a 76mm Sherman? Yes, it is more tactically mobile then both, but strategically that advantage is not really noticeable. The ballistics are the same on all three, but the armor is weaker than the other two. All it has over the M10 apart from mobility is a lower profile and a power traversing turret. And the M10 even has some advantages, more ammunition and a bit better armor. Against the 76mm Sherman, it really only has mobility and profile, but it loses so much flexibility with its weak armor. If compared to the M36, it only has mobility and profile. And mobility simply doesn’t matter as much as Lt Col Bruce thought it did.

As the war went on, there were a few trends in the employment of tank destroyers. They all had to do with increased coordination with other branches, being used in the active support role of armor and infantry, and using them in frontline combat as opposed to holding them in reserve to thwart attacks. In all, they started being used more and more as tanks than tank destroyers. With these trends identified, the Tank destroyer doctrine was disproved, and the TD’s largely scrapped. The idea was a failure.

But the M18 wasn’t. Is it a paper tiger? Maybe. But as far as the tanks that have this reputation go, this ones gotten the closest to meeting it.