Tank Battles

I wrote earlier about bringing enough gun to the fight, but not too much. A prime example of this was the M-1 Abrams tank.

When this tank debuted, people were aghast at the cost. What they didn’t realize was it was acutally the result of an extreme cost cutting program. For 20 years, the Army had been cooperating with Germany to develop a sucessor to the M-60 series of tanks, but each iteration had become too complex and too costly. The Army finally decided that they would develop a tank using technology shared with the Germans rather than develop a tank to be used by both countries.

One of the sticking points was the main gun. The standard US tank gun was the 105mm M68. The Army thought this was sufficient to defeat current and projected Soviet armor (and were pretty much right).

The Germans had developed the excellent 120mm smoothbore, and wanted both countries tanks to use it. Our Army resisted for a couple of reasons. The biggest was cost. The new gun would have to be license produced here, with associated setup costs. Even more expensive would be providing stocks of ammunition for the gun. The Army had a huge stockpile of 105mm ammunition already. Buying an entirely new stockpile in the tight budgets of the 1970s wasn’t an attractive option.

In the end, the 105mm won-sort of. The decision was to place the M-1 into production with the 105mm, but make provision to add the 120mm in the future. As it turned out, for various reasons, this was a lot harder than anyone expected. Still, partly as a sop to our German allies, and partly over concern about the ability of the 105mm to defeat future Soviet armor, the 120mm was adopted for the M1A1 that entered service in 1988.

One disadvantage of the 120mm was a reduced ammo load. An M-1 with the 105mm carries 55 main gun rounds. An M-1A1 carries 40. As it turns out, however, few tanks will shoot their entire basic load in a single battle. In fact, not a single tank in Desert Storm fired its entire basic load.

Tankers, ever wonder why the coax on your tank has that massive 4000 round load? Because that’s where the designers originally wanted to put the 25mm M242. The only reason it didn’t make it into the final design was cost. Leaving the 25mm out saved about $100,000 just for the gun, and made the fire-control system simpler, and hence cheaper. 

10 thoughts on “Tank Battles”

  1. Hey Xbrad,
    You are posting up a storm, and good stuff too.
    In my personal list of cool sh*t ships with guns and missiles are first then tanks. Big booms. How long is the 25mm? Looks pretty darn big.

  2. V,
    Barrel length (old style barrels) is 85″, plus the receiver, so total is only about 9-10′. Weighs about 250lbs.
    Normally, you take the barrel off (it’s a quick release like most machine guns), and then pull the reciever out from inside the turret through the back of the track. If you have to though, you can pull the whole gun backwards. Major pain in the ass. Not so much because it’s heavy, but because it is such a tight space to work in.

  3. As long as I am asking questions and you are answering, What is similar to a 25mm HE? Explosive wise, more or less than a 40mm? How does it compare to a standard hand grenade?

  4. V, the actual HE projectile (HEI-T, actually) is roughly the size of your thumb. The bursting radius is listed as 5 meters. You can expect a target within 5 m of the impact to get some fragmentation. Since the gun carried 230 rounds of HEI-T in the ready ammo cans, we tended to fire quite a few.

    A typical burst would be one shot to determine the range, then a three round burst on target. rinse and repeat. This would be for a point target like an ATGM team, a truck, or a sniper in a building. For an area target, you fire a Z-pattern. Select the low rate of fire, 100 rpm, and fire a continuous burst left to right, then right to left while increasing the range, then left to right. Sorta spray and pray.

    There’s only 32 grams of explosive filler in the round. As the caliber of round increases, the filler increases exponentially. A 40mm projectile, for instance, weighs about 2 pounds, and about half that would be explosive.
    A hand grenade (M67) weighs 14 ounces. About 6.5 ounces (184 grms) of that is explosive. But I can’t throw a grenade 30 football fields away.

  5. Thanks Xbrad,
    32 grams out of 454 + 1/10th (not quite) so a 40mm is a bigger bang than a hand grenade? 184 vs 220? I did not know that. Thanks! I have wondered how it all fits together, but 5m is not a bad radius do you know what the radius of a M67 is? how does that compare?

    Thanks
    Vmax

  6. V, oddly enough, grenades are listed as a 5m radius as well. It’s not an exact science.
    And when I was talking about 40mm, I was talking about a high velocity 40mm, like in WWII. The two different types of 40mm grenade launchers out there are quite a bit less powerful. Again, think roughly in the hand grenade range.

    M-203’s launch a low velocity grenade out to about 400m. Mk19s launch a somewhat higher velocity grenade out to about 2000m. They are all a little smaller than an M67, but have the big advantage of standoff.

  7. I can understand that 184 vs 220 being equal, but 32 = 5 meters and 200 = 5 meters?
    What is the next step up? A mortar? They come in 60 80 and 120 right? How do they compare? Am I missing something? Is there a bigger grenade than the 40mm?

  8. Like I said V, it isn’t an exact science. I’m just telling you what the book says when it comes to burst radius. Part of the difference is that a M67 throws fragments, while a 25mm HEI-T is mostly throwing incendeary material.
    Mortars in our Army come in 60mm, 81mm, and 120mm. The 60mm isn’t a very fearsome weapon. Many times, it’s used more to lay smoke or fire illumination rather than to try to blow up the bad guys. While the 81s and 120s also do smoke and illum, they are quite a bit more likely to be effective at killing people.
    The big advantage to a mortar system is that it belongs to you, and so is very responsive, rather than having to call a higher headquarters to get field artillery. Some folks refer to it as the commander’s “hip-pocket artillery”. Each infantry company has its own mortars and can get them shooting in about a minute, rather than calling for artillery and having to wait for five minutes.
    The only grenade size used in grenade launchers in the US is 40mm. Understand that these aren’t so much grenades like you throw, but rather, low velocity explosive shells. A 40mm grenade for an M203 looks like a giant 9mm round.

  9. Depending on what I’ve eaten, and how it settled, the merits of the Leopard II vs the Abrams can vary and the Merkava is very interesting also. Crew training and alertness probably counts for more than the technical differences.

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