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HEAT-T/MPAT Super elevation angle


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HEAT-T/MPAT 120mm super elevation angle

Just a quick observation on the appearance of the time of flight and super elevation angle. I have noticed that when firing HEAT-T (105mm) and MPAT 120mm the super elevation angle seems to be really exaggerated. The flight time at 1600m also seems odd. Its appears quite honestly to look light a 155mm round in flight. I am currently looking for the 120mm firing tables to determine the actual Line of Sight (LOS) and super elevation angle is for this round. If I am not mistaken the normal velocity for M830 (HEAT-MP-T) is 1140 meters a second (3,740’ per second) and M829A1 (APFSDS-T) normal velocity is a round 1600 meters a second (5,512’ per second). I have witnessed firing both at a range of 2000m (in real Life) that the super elevation angle between the two only deviated by a few mils in elevation when observed through the GPS. The flight time by the observer was also minimal.

Note: We would normally not engage targets with MPAT or HEAT beyond 2000 – 2200 meters due the instability of the round and it becoming sub-sonic.

I may be wrong on this issue as it has been over 12 years since I crewed an M1A1.

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This seems to ignore the deceleration due to air resistance, and the increased path length due to superelevation.

From kotsch's web page:

HlPat87 (afaict = DM12A1 ~ M830)

1000m, 1.00 s, 4.6mil superelevation

1200m, 1.23 s, 5.7mil

1500m, 1.60 s, 7.6mil

2000m, 2.30 s, 11.1mil

2500m, 3.11 s, 15.6mil

3000m, 4.07 s, 21.1mil

For comparison -

PfPat87 (afaict = DM33)

1000m, 0.62 s, 1.9mil

1200m, 0.75 s, 2.3mil

1500m, 0.94 s, 2.9mil

2000m, 1.26 s, 3.9mil

2500m, 1.49 s, 4.9mil

3000m, 1.93 s, 6.0mil

SlsGr 95 (HE-T)

1000m, 1.51 s, 10.4mil

1200m, 1.86 s, 12.9mil

1500m, 2.41 s, 17.0mil

2000m, 3.45 s, 25.0mil

2500m, 4.65 s, 34.6mil

3000m, 6.04 s, 46.6mil

Image shows the variation in superelevation between M830 (upper reticle) and M830A1 (lower reticle) firing using the Leopard 2A5DK, GPS for ranging, and GAS set to range = 0. APFSDS would be slightly lower again, but I haven't made that 'engagement' and added this third reticle.

M830-M830A1.jpg.e067a13e00a3609cb40d1269

M830-M830A1.jpg.e067a13e00a3609cb40d1269

Edited by GH_Lieste
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So true, totally agree..............HEAT-T becomes subsonic around 2000m. My point is that the flight time and high angle of the HEAT round at targets at 2000 and below seems extremly exagerated, I can never remember sitting there looking through the GPS and waiting for the impact. Its all good, excellent sim.:)

p.s and the folks here are great, glad I joined

Edited by ottoramsaig
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I believe that in the M60A3 and M1IP that the Gunners auxillary sight allowed for the use of 2 reticles. One was APFSDS on top with HEP on the bottom, the other was got HEAT-T. But I still don't think it took that long to hit a staionary target at 1200 meters.................cheers

I guess my question is: Is MPAT or HEAT-T truly represented in the sim?

Edited by ottoramsaig
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I have the 120mm firing tables. I will look it up. What I do know is that HEAT (M830) beyond 2200m is unstable in flight. Between 2200to 2300 meters there is a wobble due to the shape of the round and other factors. From that point it is any ones guess on the accuracy of the HEAT round. Once it goes through the wobble, it sill maybe on gun target line or off. It will start going sub sonic at the 2200 meter point.

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M830 != MPAT; MPAT is the M830A1. Comparisons with the M830 must inevitably fail due to an apples and oranges condition. I also doubt that the M830 or DM12A1 go subsonic after 2200m already. The muzzle velocity is 1140m/s, that's almost 3.5 Mach. This would require a velocity drop of almost 370m/s per 1000m, a ginormous value. True, it's not a KE dart, but still.

At the master gunner's course the DM12 was the preferred round at long range because it is the KE exercise round that starts to wobble at around 1800m (it's designed to do that to cut down safety ranges).

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The above firing table shows that HEAT-T (DM12/M830) is still at nearly mach 2 at 2km.

M830A1 (MPAT) should be considerably faster still - it starts 280m/s faster, and should lose velocity at a lower rate, being a narrower, more streamlined shell.

What you may be confusing is TP-T and TPCSDS, the two training rounds - the TP-T (Blue painted HEAT) has no tail, and I would expect it to destabilise at some intermediate range. TPCSDS (Blue painted Sabot) has a cone stabilising tail, in place of the fins & slows rapidly and becomes unstable within the engagement range of the FCS - the maximum flight range is only 8km compared to the 120km+ for APFSDS.

Sensitivity to range finding, and difficulty in predicting target motion for significantly more than 2 seconds are probably the reasons for avoiding point-target engagements with HEAT at longer ranges, rather than a significant increase in dispersion - which should show up in the firing table, and doesn't.

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The wobble for the M830 HEAT was taught at the US Army Master Gunners Course. I will have to check the firing tables concerning the sub sonic. To me whether it was sub sonic or not at 2200 meters does not matter. I do not care. What does matter, if the warhead develops a wobble and the accuracy falls off at 2200 meters, I do care. That is what I need to know to engage targets with the proper ammunition to achieve a high probability of a first round kill.

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What you may be confusing is TP-T and TPCSDS, the two training rounds - the TP-T (Blue painted HEAT) has no tail, ...

That would be the M831A1 TP-T. I am surprised about this, but the photo in Jane's Ammunition Handbook confirms that you are right about this. This would indeed explain a loss in in-flight stability. Interestingly the 120mm x 570 DM18A2 (the target practice equivalent to the DM12) does have a tail fin assembly, which explains why we still achieved first-round hits at 3800m range. I daresay that both DM12A1/A2 and the M830 are probably stable throught the first four kilometers, even though it probably doesn't make much sense to fire it at ranges beyond 2500m if the target is small, and/or moving.

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The wobble for the M830 HEAT was taught at the US Army Master Gunners Course. I will have to check the firing tables concerning the sub sonic. To me whether it was sub sonic or not at 2200 meters does not matter. I do not care. What does matter, if the warhead develops a wobble and the accuracy falls off at 2200 meters, I do care. That is what I need to know to engage targets with the proper ammunition to achieve a high probability of a first round kill.

Master Gunner school is were I heard about the unstability of HEAT-T but that was for the

105mm. I heard it mentioned after that while attending the M1 and M60A3 Tank Commanders course. I would prefer to battlecarry sabot at all cost but as we know METT-T sets the ammo. When in desert operations, we would mostly load out with APFSDS in the ready with a few in storage racks.

Edited by ottoramsaig
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