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"Tank and AT Gun Firing Tables" Topic


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World War Two on the Land

670 hits since 28 Jan 2019
©1994-2019 Bill Armintrout
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Mobius28 Jan 2019 9:20 a.m. PST
Schogun28 Jan 2019 12:17 p.m. PST

Excellent! Thanks.

Steve Wilcox28 Jan 2019 12:24 p.m. PST

Very nice!

Personal logo Herkybird Supporting Member of TMP28 Jan 2019 3:33 p.m. PST

Interesting! Thanks!

Mark 128 Jan 2019 4:38 p.m. PST

A very useful assembly of information there, Mobius. Thank you for your efforts!

If you would be so kind as to share what additional depth you may have, there is at least one question that rises to my mind from the tables. In particular, the UK table.

I see entries for 2pdr APHV (mv 2800fps), and separate line entries for Littlejohn Adapter Mk I and Mk II (mv 4200fps and 3875fps). These separate line items seem to come from differing tables in the same Ordnance Board report, if I am reading your footnotes correctly.

So I am wondering: is there is any information in the OB report to identify the ammunition used in the Littlejohn Adapter tests? Was the line identified as APHV the same round used in the Littlejohn firings, or was there a different load for those firings?

My reason for asking is the working hypothesis, which I have seen discussed and reasonably well supported, that the Littlejohn adapter itself (as well as the whole squeeze bore principal) was a red herring. That it was the high pressure load of the cartridge, and the light weight projectile (with a small bore dense core) that generated high muzzle velocities. This is why a sabotted rounds typically achieve the similar velocities as squeeze bores, without the squeeze.

If that is so, it should be visible in muzzle velocities of test firings of the 2pdr gun shooting the same round with and without the adapter fitted. If such comparative data is available. Which is why I ask. Am I seeing such a case here (if so, it very clearly refutes the hypothesis above), or am I seeing dissimilar rounds on the various line items?

Just curious.

-Mark
(aka: Mk 1)

Russ Lockwood28 Jan 2019 5:51 p.m. PST

Cool. Great compilation.

Mobius28 Jan 2019 6:07 p.m. PST

No, the Littlejohn tests were separate OBs. Maybe I didn't read them correctly. Over at the Axis History forum I asked for someone to post the OBs.
https://imgur.com/5aGYsgY
https://imgur.com/a/lGV4IFu

Mobius29 Jan 2019 5:46 a.m. PST

OK, now I get what you mean Mark. APHV (high velocity) was just the name for the 2-pdr shot fired at 2800 ft./s instead of 2600 ft./s. It was not a hyper velocity shot.

Wolfhag29 Jan 2019 4:00 p.m. PST

Mobius,
The penetration figures for the German 75L70 are about 10% less than what is shown in Bird & Livingston's book. What causes the discrepancy?

Wolfhag

Mobius29 Jan 2019 5:35 p.m. PST

For one thing the penetration is per 270 BHN hardness armor. Bird and Livingston base it on 235 BHN hardness armor. 235/270 BHN = 0.929 armor quality.

Plus the ballistics may be wrong. Somewhere I read the that was somewhat based on Dheil's tables from AFV-G2. Unfortunately that was based on an 'Aberdeen' table. But, Aberdeen didn't put out tables in meters which that table used. So Dheil mixed meters for yards. A third reason is it may use the British CV/48 (??) 75mm small capacity graph has the MV of 3110 ft/s for the 75mm KwK 42 not as the true MV of 3068 ft/s.

I have an entire page on the differences with Russian guns.

Wolfhag29 Jan 2019 6:08 p.m. PST

Thanks. That's some good work.

I'm trying to use original sources when I can. Is this Russian data verifiable?
link

I like the B&L data because it shows penetration at 0 degrees.

Thanks,
Wolfhag

Mobius29 Jan 2019 6:48 p.m. PST

The 100mm BR-412 is pretty close. Like the 1944 striking at 1000m is 741 m/s but the 1962 striking at 1000m is 739 m/s.


My normalized data is also at 0 degrees,

Wolfhag29 Jan 2019 8:52 p.m. PST

Thanks. That's some good work.

I'm trying to use original sources when I can. Is this Russian data verifiable?
link

Thanks,
Wolfhag

Wolfhag31 Jan 2019 7:28 a.m. PST

I'm not sure how that last post got there. Maybe when I rebooted.

If the B&L penetration data is for armor with a specific hardness would there be a way to modify armor with higher and lower hardness? Would higher hardness be harder to penetrate but a greater chance of spalling and lower hardness greater chance of penetration but less chance for spalling?

Wolfhag

Mobius31 Jan 2019 8:58 a.m. PST

Yes. In general that's how it works. The harder armor can also crack. Then there is other things like shell shatter and break-up or ricochet on harder armor. Variation in shell nose hardness and strength also complicate matters.

I've found that a large part of the penetration factor of B&L or even WWII Russian data is based on their ballistics. If that is wrong then their calculated numbers are wrong. Most of the Russian data is calculated with the DeMarre formula using K=2400.


Since the B&L book was published a lot of new information has come out on the ballistics of Russian guns.

Wolfhag01 Feb 2019 8:15 a.m. PST

Yes, lots of new stuff for the Russian guns but some of it is still confusing.

I have the trajectory tables for a number of US, German and Russian guns so I don't need my formula to figure out the accuracy levels.

So if I wanted to modify armor based on BHN over and under B&L 250 BHN: For every +/- 15 BHN there would be a +/- 5% armor modification. I already have a way to determine spalling damage from non-penetrating hits against brittle armor.

At what level of BHN is armor determined to be "brittle"?

I know it starts getting complicated when you need to take into account T/D ratios, overmatching and shell nose brittleness, etc but I'm just exploring different ways I can take some of these factors into account and keep it fairly simple.

Thanks,
Wolfhag

Mark 101 Feb 2019 10:11 a.m. PST

So if I wanted to modify armor based on BHN over and under B&L 250 BHN: For every +/- 15 BHN there would be a +/- 5% armor modification.

I fear that this approach is too simplistic.

I would not react positively to any detailed ruleset that has a simple construct of "harder = better", even if there is some threshold point at which shatter or cracking starts to work it's way in.

The problem is that harder = better against SOME projectile types. And harder = worse against OTHER projectile types.
And hardness is not always homogeneous.

Early- and mid-war German hardened armor, up to about 50mm (and in limited cases 80mm) of depth, was usually face-hardened. In this formulation, the face is quite hard, but the depth of the armor is softer and more pliable. This form of armor does not suffer the shatter effects, providing high potential to "bounce" an uncapped projectile, but still proving ductile in the case of partial penetrations or over-matching. For thicker plates (Tiger), and in late-war once costs, capacity, and availability key alloys became dominant factors (Panther), the plates were not face-hardened.

If it was simply harder = better, then many nations would just have used harder armor. It isn't that hard to make armor hard. The Soviets took this approach. It was not very productive for them.

Capped (soft nosed blunt caps over pointed hard core, not just ballistic capped) projectiles often perform BETTER against harder armor. Blunt-tipped projectiles, with very high hardness (and a ballistic cap) can also perform better, depending on other variables.

By mid-war, British AP projectiles usually were typically APCBC (AP capped, ballistic capped) in construction. This negated, and in many cases reversed, the benefits of hardened armor. Soviet projectiles went through numerous progressions from 1941 to 1944, from pointed to blunt with ballistic caps to pointed with soft blunt caps and ballistic caps.

Part of the problem of US AT projectiles in the early war period was that US Army Ordnance was behind on this topic. The M79 AP rounds (solid shot), per US Army Ordnance, had superior penetration to the M61 APCHE rounds. But the M79 was a pointed projectile, while the M61 was blunt with a ballistic cap. M79 showed a distressing tendency to ricochet (to "bounce") at reasonably low angles against hard German plate that it should have penetrated. M61 was more likely to dig in and penetrate. But … the hardness of the M61 was inconsistent, and the shell walls would often collapse, leading to failures against face-hardened armor (with a high hardness surface, but a ductile depth).

I don't think there's a simple formula. It's either a complex formula, or it's a large matrix of myriad "this projectile vs. that type of plate".

At least that's what my readings have shown me.

-Mark
(who is not now, nor has ever claimed to be, a game designer)

Mobius01 Feb 2019 11:34 a.m. PST

Mark is right there is a lot of complexity of shell and armor comparisons.
Though armor hardness within certain limits can be compared as a ratio. In a small scale test a hardness quality ratio can be made.
PDF link

Penetration for homogeneous armor generally consisted of splitting the armor and producing pedals on the far side. Penetration of face-hard armor consisted of punching out a shell sized plug of armor. Less energy is required to punch out a plug though the shell has to remain intact. Often it would breakup or shatter without an AP cap. Russian armor was outside the normal range of hardness for homogeneous armor. Their high hardness was not face-hard but required a plug of armor to be punched out to be penetrated. It proved very effective in defeating early war German AP shells (Pzgr. Patr.). Once Germans figured out how to make hard capped and hard nosed shells (Pzgr. 39) that armor proved a liability.

At the Axis History Forum they have several threads going on this subject.
link
link
link

-Mobius

Wolfhag01 Feb 2019 1:19 p.m. PST

Thanks guys.

I considered the hardness factors et all and blunt-nosed rounds quite a while back but decided it was too complicated. Some of the playtesters, after reading up on some of it, asked about including it (a little knowledge can be a dangerous thing) so I said I'd check to see if anyone had a way to handle it.

If you are not going to include hardness/brittleness then what BHN should you base your armor penetration values on that would work for all of WWII?

At what level of BHN is armor determined to be "brittle" and start having problems with spalling? In the book about a Soviet crew that had Shermans said they never experienced the spalling damage that his T-34 comrades experienced.

I have not done anything for N. Africa but it would be good to include FH armor against non-capped AP.

Wolfhag

Lion in the Stars01 Feb 2019 7:54 p.m. PST

I remember seeing a discussion about BHN of Sherman armor versus T34 here on TMP. Was a report about how the Russians didn't like the armor steel they were being sent from the US, it was too brittle when hardened like the steel they were used to.

It may have been a Tango post. I've looked back to September 2018 and haven't found it. Maybe someone else will have better luck?

Wolfhag04 Feb 2019 10:48 a.m. PST

I think I'm going to use a BHN of 320+ as "Brittle" armor that has a greater chance of spall damage from a non-penetrating round.

I'm using a penetration of > 110% (over penetration) causing full internal damage. Penetration of 100%-110% can be a full or partial damage. Penetration of 5mm-10mm < armor causes spall damage.

Wolfhag

Personal logo Mserafin Supporting Member of TMP07 Feb 2019 10:48 a.m. PST

These tables don't seem to include data for hollow-charge rounds, at least as far as these old eyes can tell. Does anyone have data for those, particularly German?

Mark

Mobius08 Feb 2019 7:35 a.m. PST

You can find German data on German guns on this site:
link

Personal logo Mserafin Supporting Member of TMP08 Feb 2019 10:25 a.m. PST

Thank you, Mobius!

Mobius08 Feb 2019 10:54 a.m. PST

Thanks for pointing out the missing HEAT rounds. I added that to my data tables. I just didn't have the values in my penetration averaging program.

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