The M1 Helmet

Here's another bit of modern-ish-day armor, this time for your dome.  I'll be taking a multi-factorial approach to the classic M1 helmet of World War 2 fame, analyzing it in the same manner I had in a few earlier posts on ballistic protective equipment.

GURPS High Tech provides guidance on this helmet on p70.  I am not trying to refute it.  Rather, I am analyzing this because it felt weird to do a few contemporary body protections without "completing the set", such as it is.

The M1 Helmet

The M1 Helmet was adopted by the United States in 1941, to replace the older M1917 helmet of WWI fame.  More than 22 million olive drab "steel pot" helmets were produced by 1945, and between 1966 and 1967 another million (with an improved chinstrap and lower profile) were added to circulation.  The helmet would serve in mainline US forces until it was replaced by the PASGT helmet in the early 1980s, but wouldn't really leave service completely until sometime in the 1990s - at least a small number of troops on the ground in Desert Storm can be seen wearing these.  The helmet would be used either directly by or as an inspiration for the helmet in many other nations.  Examples include Germany and Israel (direct users) as well as Argentina (localized copy).

The M1 helmet is actually a system that comprises two basic elements:  A non-metallic "liner" that doubles as mounting for the suspension as well as a lightweight non-combat duty helmet, and a manganese-steel shell.  The liner can be worn alone, but the steel shell is not intended to be - rather, it is designed to sit on top of the liner.  Both of these elements have their own chinstraps, but only the liner has something to keep it off your head - originally a canvas suspension, but replaced later nylon.

What keeps the two together kind of varies based on the user.  If you're doing it the approved way, your liner chin strap is slid up over the top brim of the shell, and the shell's chinstrap holds the entire assembly to your head.  However, troops under the impression that their necks could be snapped by shell blasts if the helmet was strapped on folded both the chin straps over the forward and rear of the shell and liner to sort of strap them together and allow the entire assembly to just rest on the head.  It is worth noting that the liners between the two production runs aren't exactly interchangeable.  They can be made to fit, but the draw was different on each.


Speaking of the chinstrap, in 1944 the straps were upgraded with a new latch.  This would yield under 15lb of force, allowing helmets to be blown free in case of shell blasts or if someone tried to grapple the helmet and use it as leverage.

The primary purpose of this helmet is to protect a soldier's head from shrapnel, much like some of the body armor that served within the same temporal scope that this helmet did.  But, much like those armors, it seems like it is capable of resisting more than just shell fragments.  The steel shell was a single piece of pressed manganese steel that started life as a .43" thick disc.  Pressed into shape, the helmet's vital bits - brow and front of the dome - came in at about .035", thickening around the brim slightly, and thinning around the back slightly.  This gives the helmet an average thickness of about .035", and a weight of 2lb 8oz.  Cost in 1943 was $1.05.

The liner was .0625" of resin-fiberglass impregnated canvas duck cloth (at least, the vast majority were - very early on they were resin-pressed paper!).  It weighs 10oz, and cost $1.98 in 1943.  I guess that speaks to the relative development of these two industries.

According to tests run by the Watertown Arsenal Laboratory in early 1945, the helmet shell was actually capable of resisting .45 caliber ACP rounds at 25'.  Results depended on if they used a gilding-jacketed soft-core or a copper-jacketed hard-core round - ballistic limit for the former seems to be at 911 fps, with the latter at only 735 fps.  It seems like the harder round's impacts were pushing the limit, with more "partial penetrations" than the softer one.

The liner was not so good.  In basically no cases did it offer up credible resistance to the .45 cal test projectile.  If the shell was breached, the liner was as well.  Probably all it would do in the context of such a massive projectile is perhaps reduce marginal cases of blunt trauma where deformation was more excessive than desired, but not breaching the shell completely.

It is probably worth noting that the barrel used in this test is actually one from a M1921 Thompson Sub-machine Gun (the firing apparatus itself being a modified M1903 Springfield bolt action).

Poking about online, I see anecdotal evidence of them resisting .38 caliber handgun rounds reliably (with denting), and some 9mm as well, though less reliably.

The M1 Helmet in GURPS

High Tech mentions this helmet on p70.  It is an example of the generic "TL6 Medium Helmet", and it has DR4 to the Skull for 3lb.  It mentions that the liner can be worn on its own at DR1, which implies the shell itself is DR3.  Let's take a look at that - do the numbers hold up?

GURPS RAW

Well, we are told in HT that a .45 M1911 Thompson is 2d+1.  This is what I expect a comparable firearm to be, as the bullet and barrel length are the same as the test apparatus the Army was using around the time this helmet was coming about.

That would be DR8 ((3.5*2)+1) for the helmet shell.  Much higher than what HT supposes, which is interesting.

The liners weren't themselves shot at so I don't have anything for you here.  We do know the liners didn't offer any real ballistic protection against the projectile so we're probably looking at DR0, at least against pi type attacks.  That said it does appear to be convention to offer any kind of protective stuff as having some kind of DR minimum, so DR1 is probably just fine, moreso against Cut and Crush damage types.

Terminal Ballistics

A 230 grain projectile traveling at up to 911 feet per second would result in 2d+1 penetration.  This is the same as the M1921 SMG given on HT124, and represents the ballistic limit of the "soft lead" projectiles with a gilding jacket.

The same projectile going only up to 735 feet per second deals only 1d+3.  This is the ballistic limit of the "hard lead" projectile with a copper jacket.

The average of the two in velocity is working out to 2d - the same as the 1911 Colt Government on HT101.

So DR is anywhere between 6 or 7 (rounding on 6.5) and 8.  Again, this is higher than the generic example would suppose.

The sticking point in this model is soft core vs hard core and the jacketing type.  The harder core copper jacket round would seem to be regular FMJ.  The other is behaving a little like JHP, but it isn't actually one.  Perhaps it would increase DR by a span - seems like roughly 20%.  Conversely, maybe the hard lead version deserves a small armor divisor?  At this point, I do not know.

With that in mind, I'm inclined to select DR7, as it falls between the two DR samples and skirts the hard-or-soft-lead issue a bit, as well as acknowledging that a 6.5 average would be taken as 7.  Though, it's worth nothing that 1d+3 results in an equal chance of any result between 4 and 9 (16.67%).

The liner is actually tested on its own with and 8lb iron ball dropped 3' onto it.  This will be 4" in diameter, and working that through the Terminal Ballistics formula gets me 0d+1, which fits in with the predicted DR1.  I would suppose that this really should only give DR against Crushing (and probably Cutting) damage types, however, as the tests with the .45 suggested that it offers basically no resistance to bullets.

Cutting Edge

I would assume that the shell counts as TL6 "High-Strength Steel" due to the reference to homogeneous nature and the fact that other steels around this TL are "face hardened".  That material is worth DR70 per inch, with a maximum of DR14.

On a .035" average thickness, we see: 70*.035 = 2.45.

As the convention is to round down in these cases, we see a helmet shell worth DR2.  Not very far off what's given in HT.  If you bump the thickness up to the maximum in the test set (.038) you find DR creeps up to 2.66, high enough for DR3.

The liner is .0625" thick, and is probably described as ballistic resin, though that is a "late TL7" invention according to Cutting Edge.  DR15/in, max DR6.  That would result in .0625*15 = .9375.  Close enough to count as DR1.

Helmet Accessories

The helmet was associated with a couple of accessories.

The US Army issued an official net - the M-1944 - which reduced shine off of the helmet and allowed the attachment of camouflage.  There were a few netting types - adopted from the Canadians - in use prior to this being given a type designation, often cut from actual nets.  These official models made a debut right at the end of 1944 or very early 1945.

Netting would eventually be replaced with a number of covers, reaching widespread issue sometime between 1945 and 1950 (though early versions began to show in the Marines sometime around 1943).  These are essentially a tailored cloth attachment that fits around the helmet.  They are sometimes just OD green, but usually have some kind of pattern, such as EDRL or Mitchell.  They usually have slits and a forehead band for inserting more foliage as camouflage.

A mosquito net attachment that covered the helmet and looped under the arms was produced, but evidently not issued in any real number.

See Stealth and Camouflage on HT76 for ideas on handling these.

During the Vietnam War, the AN/PRR-9 became available - a helmet-mounted radio.  Though it is apparently mostly plastic, I can't imagine that felt very good on the head.  This is probably why when I do see this thing in photos, it is usually attached to someone's webbing, rather than their cover.

Summary

 

Notes on Weight and Cost

As before, it was rather inexpensive to produce these - $1.05 for the shell, and $1.95 for the liner (in 1943 anyways).  This was surprisingly low, and translates up to $11.47 for the shell and $21.62 for the liner if you are talking the standard 2004USD that GURPS uses for its frame of reference.  I suppose it makes sense, given how WW2 industrial contracts worked - something with such a vast quantity required probably couldn't be allowed to cost much per unit.

Weight is that of the real helmet and liner; variance was within an ounce or two either way.  High Tech was pretty much spot on with that metric at 3lbs.

Other Considerations

This helmet seems to have interacted poorly with the M69 Fragmentation Protective Vest when the collar was turned up and the user was prone.  The collar and rear of the helmet do not play well together, so it is difficult to raise your head to look forward and keep your helmet on right.  There seems to have been the same issue with the later PASGT vest as well.

The shell is a utility item - it can be an improvised shovel, a cooking pot (which could anneal your helmet and reduce DR), a water carrier, a shaving bowl, or just about anything a scoop-like object could be.  My crude math gives me about 1500 cubic inches - 7"x11"x9.5".

If a character is in the camp of keeping the helmet loose on their head, you should probably keep that in mind whenever something could potentially knock it off.

The liner is worn on watch in low-danger areas (such as fire watch) and sometimes as a bit of a unit trademark - up until the mid 2000s, US Navy SEAL candidates at BUD/S school wore these helmets.

Closing

An interesting little exercise, and like some of the body armor I've done in the past shows where a potential disparity can arise between the DR/inch assumptions of Cutting Edge or Basic Set and what we see in reality.  As before, this isn't to denigrate either system, but rather to highlight different frames of reference.  Hopefully this one was more quick and concise than some of my earlier dissertations!

This helmet model (or those very much like it) is one of the most common in use within less advanced military forces in my Tiberian Dawn game setting.  Nod itself uses them for units that do not serve on the front line (supply troops, engineers, etc), and passes them out among the militias as well (being more common than body armor in most cells).  Most Nod-actual combat units have, by the outbreak of the war, more-or-less transitioned to using more advanced ballistic helmets.  Actually, a lot of helmets like these turn up in GDI ranks towards the end of the conflict, as their model of mass-levy and rapid training far outpaces their reserve stocks of more modern ballistic defenses.

Thanks goes to the US Militaria Forum for help in finding details beyond what was cited via hyperlinks in the article.  It is amazing what they can turn up.

And thanks goes to you, my readers, for dropping by and reading things I write.  Even if you don't use these things directly, hopefully it can inspire you to create something you need.

Thanks for reading!

Cheers!