Documentation of M1A2 / M1A1 HC Hull Armor Composition (1996–2016)

Machinery of War Discussion Ground Vehicle
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I have spent the last week digging through the U.S. National Archives, NRC Dockets, and DTIC Technical Reports to clear up the confusion regarding the “Heavy Armor” package on the M1A1 HC and M1A2 series.

There is a common misconception that Depleted Uranium (DU) armor was strictly limited to the turret or to a small number of experimental hulls. However, when you cross-reference the production records across five different U.S. Federal Agencies (Army, Congress, NRC, DLA, and DOI), the documentation tells a very different story.

Below is a compilation of 5 Primary Sources establishing that DU Hull Armor was standardized for the M1A2 and M1A1 AIM fleet starting in 1996.

1. Defining the Terminology: What is “Heavy Armor”?

First, we have to establish what the Army actually means when they say “Heavy Armor System.” This isn’t a vague adjective; it is a specific program name defined in the Federal Register.

Source: Federal Register / Vol. 63, No. 134 / July 14, 1998
Agency: Department of the Army
Direct Link: https://www.govinfo.gov/content/pkg/FR-1998-07-14/pdf/98-18674.pdf

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The document explicitly defines the “M1 Abrams Main Battle Tank (MBT) Heavy Armor System” as the “depleted uranium (DU) armor package.”

Crucially, it confirms mass production status. It states that in 1996, the design change was “cut-in to production… effective with Job #1 M1A2 Phase II.” This confirms that DU “Heavy Armor” became the factory standard for the M1A2 line in 1996, not an experimental run.

2. Location: Is it in the Hull?

Once we know “Heavy Armor” equals “DU,” we check the location.

Source: U.S. Federal Docket DOI-2021-0013
Agency: U.S. Department of the Interior / Wyoming Mining Association
Direct Link: https://downloads.regulations.gov/DOI-2021-0013-0995/attachment_1.pdf

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This legal submission to the Department of the Interior regarding the end-use of uranium states:

“Some late-production M1A1HA and M1A2 Abrams tanks built after 1998 have DU reinforcement as part of the armor plating in the front of the hull and the front of the turret.”

This matches the timeline of the M1A2 SEP (1999) and SEP v2 (2005).

Corroboration:
Source: The Army’s Future Combat Systems Program and Alternatives (2006)
Agency: Congressional Budget Office (CBO)
Direct Link: https://www.cbo.gov/sites/default/files/109th-congress-2005-2006/reports/08-02-army.pdf

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Table A-1 explicitly lists the upgrade for the M1A1 AIM and M1A2 as: “Heavy armor added to hull and turret.”

3. Performance: The 960mm RHAe Figure

Does the physical protection align with DU densities?

Source: Modeling, Simulation, and Analysis of a Weapon’s Lethality
Agency: Defense Technical Information Center (DTIC) / Naval Postgraduate School
Document ID: ADA619505
Direct Link: https://apps.dtic.mil/sti/tr/pdf/ADA619505.pdf

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On page 47, the report explicitly states:

“The MBT has the heaviest armor complement of all ground platforms and the armor
thickness of its hull is equivalent to 960mm of rolled homogenous armor (RHA).”

This figure is consistent with the massive weight increase of the M1A2 (~5–7 tons heavier than the M1A1) and the mass efficiency of DU. Another DTIC report (ADA591460 ) notes that these armors are “two to three times more weight efficient than rolled steel,” which explains how a ~650mm physical cavity can provide ~960mm of protection.

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4. The License: Addressing the “5 Hulls” Myth

There is a common misconception that DU hulls were limited to “5 tanks at Army Schools.” This is based on an expired 2006 NRC application. That limit is legally obsolete.

Source: NRC Material License SUB-1536, Amendment 10 (2016)
Agency: Nuclear Regulatory Commission (NRC)
Direct Link: https://www.nrc.gov/docs/ML1619/ML16190A098.pdf

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The Change: In Amendment 10 (2016), the NRC removed the numeric limit on hulls.

The Current Law: Items 8 & 9 authorize the U.S. Army (TACOM) to possess “Tank Turrets and Hulls” as depleted uranium armor components in “As Needed” (Unlimited) quantities.

Analysis: The Nuclear Regulatory Commission would not grant an “Unlimited” fleet possession license for DU Hulls if they only existed on 5 experimental prototypes. The license authorizes the mass-produced fleet confirmed by the Federal Register.

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And i suppose that we don’t have this in the game, now do we?

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Correct. Currently, the in-game model utilizes standard non-DU composite modifiers for the M1A2 hull.

If the material modifier were updated to reflect the Depleted Uranium composition confirmed by these documents, the protection would align with the 960mm figure cited in the DTIC report.

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if this gets accepted, nations like russia or more will get stronger rounds, newer weapons etc to make that armor useless

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I honestly prefer that outcome. That is how the actual arms race works: Armor improves → Ammo improves.

Right now, we have the opposite problem. The M1A2 hull is vulnerable to rounds from the 1980s (like DM33) or even lucky shots from autocannons/WW2 tanks.

I would much rather be penetrated by a modern 2020 projectile designed to defeat Heavy Armor than be penetrated by 30-year-old surplus ammo because the hull is artificially nerfed. At least if they add stronger rounds, the gameplay moves forward instead of being stuck with an artificial weakspot.

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Prefice: I have no issues with adding DU to the hulls of the Abrams, at all. If solid proof is found then i’m all for it. What i will point out however is some flaws in logic and source criticism i found.

I think the biggest issues with your post here is a lot of speculation and inconclusive statements. Gaijin generally doesn’t accept those in this way.

Yes, but that doesn’t automatically mean the DU is present in all the parts of the package, just that DU is present in at least one part of that package. The DU is already known and to my knowledge already present in the turrets of the Abrams that have it.

My biggest problem with this part: “Some” . There is no clear definition of if that means just some of the tanks or some of the models/versions and in those cases which ones. You are speculating both that the sentence only uses the word “some” for the first half and not the part you have made bold and that the “Some” refers to models and not individual tanks within those categories listed. You have then further speculated that this means SEP and SEPV2.

Yes, but as the first point fails to specify; is the DU present in the hull as well for those standard packages or just the turret?

Not really a valid source in my opinion, it’s a student thesis and probably wouldn’t classify as a secondary source.

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This makes no sense to me, any secret military technology would reasonably have this destruction requirement and it even lists “There is no data in the HMIS and the NSN is in an FSC not generally suspected of containing hazardous materials” just above your highlight and at the bottom “The item does not have a nuclear hardened feature or any other critical feature such as tolerance, fit restriction or application.”. To me this even (if anything) indicates no DU presence in this part.

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Thanks for taking the time to read through it and provide feedback. I appreciate you looking at the sources.

I want to address the specific points you raised because I think the context helps clear up the ambiguity.

Regarding the DOI document and the phrasing “Some M1A2s built after 1998”: The reason I don’t view this as speculation is the timeline. The M1A2 SEP v1 didn’t enter production until 1999, and the SEP v2 started in 2005. So literally every single M1A2 SEP and SEP v2 falls into the category of “M1A2s built after 1998.” The document specifies that post-1998 builds have the reinforcement in the front of the hull. Since the tanks we have in-game are from that exact time period, the statement applies to them directly.

On the logistics and NSN side: I see what you mean about the HMIS note, those are often boilerplate descriptions. However, the key piece of evidence I posted is the DEMIL Code D for the specific Hull Front Lower Plate (NSN 9515-01-532-1364). Code D requires “Total Destruction” to preclude restoration. If this plate were just standard steel or non-hazardous composite, it would typically be Code A (scrap) or a lower security code. The requirement for total destruction of that specific plate aligns with the presence of restricted materials or classified geometry that goes beyond standard armor.

As for the Naval Postgraduate School thesis, I understand it’s not a technical manual, but a Major in a Systems Engineering program at a DoD institution usually has access to validated data points. But even if we ignore the specific 960mm number, the physics still point the same way. The M1A2 is 5 to 7 tons heavier than the M1A1. That mass had to go somewhere, and since the dimensions of the tank didn’t change, the density of the armor had to increase significantly.

We have the DOI saying it’s in the hull for post-1998 tanks, the CBO saying the Heavy Armor package was added to the hull, and the Federal Register defining Heavy Armor as DU. To claim it isn’t in the hull requires us to assume that all three of these agencies used incorrect language simultaneously, which seems unlikely.

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It’s speculations because you’re attributing the word “Some” in a very specific way when it can be read differently (purely semantically).

So if you say the sentence as “Some […] M1A2s built after 1998” , meaning that you included the latter listing in the “Some” then there is no clear indication that it’s all of them. It also doesn’t specify “versions” but rather “tanks” so it could just as well be read as just some of the tanks in some of the versions have the reinforcement. And at that point it’s to vague to make any definitive statement about. I think you’re falling into the trap of confirmation bias, your finding what you’re looking for without considering other options to be possible.

To make your fault here very obvious and in the hopes of making you look at things with fresh eyes; The page you linked and are talking about here, with this statement present, is about the M113 personell carrier and not the Abrams.

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The “D” code statement likely applies to all sensitive military tech regardless of hazardous materials present or not.

It likely won’t be accepted as a source due to the naturer of the paper, it even lists it’s own sources at the end so likely to be considered a third party source. Sadly Gaijin doesn’t accept player made calculations and this is also highly speculative. There are many other places the weight could have gone.

In my opinion they haven’t, i think you have read it in one way when it can be read in a couple of ways without faltering language in the other interpretations of the sentenses.

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Those “5-7 tons” also includes the turret armor packages, as the M1A2 is less than a ton heavier than the M1A1Hc and that iirc doesnt have DU on the hull.
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I actually looked closer at that parts database link and you are right, that was a mistake on my end. I missed that it was categorized under the M113 family, so I will drop that specific NSN point.

On the semantics of the word some, I understand your concern about speculation, but in the context of federal defense reports, it is usually used to group production blocks. Since the SEP v1 and v2 are the specific versions built or upgraded in large numbers after 1998, it is logical to see them as the intended group. It distinguishes the modernized fleet from the early 1990s models.

But even if we set the semantics of that one sentence aside, we still have the PNNL-14168 report from the National Laboratory. That study explicitly states that during Phase III testing, they fired directly into a DU-armor package of an Abrams Ballistic Hull and Turret. A BHT is a production-representative test unit. This isn’t a guess; it’s a technical description of the actual hardware used in a multi-million dollar scientific safety study.

When you combine that with the Federal Register confirming a production cut-in for the M1A2 in 1996 and the CBO explicitly telling Congress that heavy armor was added to the hull and turret, the picture becomes very consistent. The physics also back this up. The M1A2 is roughly 5 to 7 tons heavier than the M1A1. Adding that much mass without changing the physical dimensions of the tank can only be explained by a massive increase in material density in the frontal arc. If that weight isn’t the heavy armor package in the hull, there really isn’t another component in the tank that accounts for that much missing weight.

I’m just trying to follow the logical chain from the different federal agencies and scientific reports. It seems more likely that they are all describing a production reality rather than all of them being mistaken about the hull.

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That chart actually illustrates the point quite well. If you look at the jump from the baseline M1A1 at 65.1 tons to the SEP v2 at 69.3 tons, you are looking at more than 4 metric tons of added mass. If you look at the SEP v3, that growth hits over 8 tons.

My argument is that this entire lineage of heavy armor tanks, starting from the M1A1 HC and AIM through the M1A2 series, represents a significant mass increase that aligns perfectly with the federal documents I provided.

The CBO report explicitly tells Congress that the heavy armor was added to the hull and the turret for the M1A1 AIM and M1A2 upgrades. The Federal Register notice confirms the production cut-in for this package happened in 1996. The weight growth you see on that chart between the M1A1 and the M1A2/SEP variants is the physical evidence of those documents being put into practice.

You mentioned the M1A1 HC doesn’t have it in the hull, but that is exactly what the new evidence is challenging. If the budget reports and environmental assessments are defining this heavy armor program as a depleted uranium package applied to the hull and turret, and the tank’s weight jumps by several tons during those exact production years, it’s a very consistent picture. We can’t really assume 8,000 to 10,000 pounds of extra material is all packed into just the turret cheeks when the official records specifically name the hull as part of the upgrade.

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First those are imperial tons, and second those includes the over 3 tons increase of the turret DU from the previous M1A1HC

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Fair enough on the short ton vs metric ton distinction, but that still leaves us with about 6,600 pounds for the M1A2 and over 8,000 pounds for the SEP v2. The M1A1 HC was already the “Heavy Common” version with the heavy turret armor, so that extra weight has to be accounted for somewhere.

If you tried to pack another 3 or 4 tons purely into the turret cheeks, the center of gravity would be shifted so far forward that the front suspension would be constantly bottomed out and the tank would be essentially undrivable. It only works if that mass is distributed across the frontal arc, which is exactly what the CBO report confirms when it explicitly tells Congress the heavy armor was added to the hull and turret.

The documents say it’s in the hull, and the physics of the weight increase require it to be in the hull to keep the vehicle balanced. It’s easier to believe the official record than to assume the Army built a tank that’s physically impossible to drive.

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Another misinformation topic claiming that non-DU hulls are in-fact DU hulls when the United States military says they aren’t.

The document you did cite was also for SEP3, not older Abrams.

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They didnt “pack” another 3-4 tons on the turret, the hole upgrade from the HC to the M1A2 is 3/4 of a ton, later on with the V3 which iirc there is pretty solid evidence of the upgraded hull they packed over 5 tons on the hull and turret armor, which did get an visually bigger array.

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Gaijin isnt gonna add it, they have decided that its a marketing lie already.

maybe if you find T-80 DU inserts too they would think about it

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You are confusing the timeline. The SEPv3 (M1A2C) did not exist when these documents were written.

The DOI Document: Explicitly states “M1A2 Abrams tanks built after 1998.” The SEPv3 entered service around 2020. The “After 1998” production run refers to the M1A2 SEPv1 and subsequent SEPv2 refits.

The CBO Report was published in August 2006 . It explicitly lists “Heavy armor added to hull and turret” for the M1A1 AIM and M1A2 . The SEPv3 would not be designed for another decade.

To claim these sources apply only to the SEPv3 requires you to ignore the dates printed on the pages. These documents describe the fleet as it existed in the early 2000s.

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That chart actually backs up the CBO report, it doesn’t disprove it. You need to look closer at the specific variants listed there.

First, look at the M1A1 SA column. That stands for Situational Awareness, which is the AIM refit program. Your chart shows it is nearly a full ton heavier than the M1A1 DU, which represents the older Gulf War standard. The CBO report I linked explicitly lists the M1A1 AIM having armor added to the hull and turret. A full ton of weight gain fits perfectly with a hull armor upgrade; electronics do not weigh that much.

Second, look at the SEPv2. It jumps up to over 71 tons. The CBO report was published in 2006, and the DOI document refers to tanks built after 1998. That covers the entire SEPv1 and SEPv2 production run.

So you have a 71 ton tank in 2006, and a Congressional report from 2006 stating that the government is paying for heavy armor in the hull. The chart just confirms that the mass exists to support what the documents say.

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The documents were written after SEP2 was in service and when SEP3 was in development.

The documents you provided talking about DU hulls were not made in 1998.
You only ever provided one 1998 document which is talking about the DU in turrets.

The 2006 document also states no DU armor in hulls. Just improved armor and gives no numbers on the new protection the standard array gives.

The first ever one to talk about DU hulls is 2014, which is a student Thesis.

“As needed” is a 2016 document, which is SEPV3:

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Read your own sources before posting, cause your sources refute your narrative.

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You are confusing the timeline. The SEPv3, or M1A2C, didn’t even enter Low Rate Initial Production until late 2017.

The DOI document explicitly refers to tanks built after 1998. That timeframe corresponds to the M1A2 SEPv1 and the later SEPv2.

The CBO Report was published in August 2006. It explicitly lists heavy armor added to hull and turret for the M1A1 AIM and M1A2. The SEPv3 wouldn’t exist for another decade. The CBO was auditing the fleet as it existed in 2006.

Regarding the license, the amendment is dated April 2016. That predates the production of the SEPv3. The NRC authorized the Army to possess hull armor for the fleet that existed at that time, which was the SEPv2 and M1A1 SA. You are trying to apply these documents to a tank that hadn’t been built yet to avoid the fact that they describe the tanks we already have.