Stardate 20020824.1325

(Captain's log): My comments yesterday about how tank ammunition and tank armor work has brought in a surprisingly large amoung of well written email, correcting a few mistakes I made and providing a lot of additional information which is interesting. I apologize for not doing more quoting, but the volume of mail on this has been impressive.

The most important mistake I made was to say that the shaped charge used in HEAT formed a jet of plasma. In actuality, the cavity in the front of the shaped charge has a layer of copper over it, and what gets formed is a very high energy stream of molten copper, which is what cuts through the armor. Chobham armor still works to defeat it the way I said, by causing the jet to spread, which blunts it. (Several different people wrote in about that one.)

Several people pointed out that HEAT actually works better with a smoothbore weapon (if you can hit) because if the round is spinning when it hits it interferes with formation of a tight stream of copper. If the stream is wider and less concentrated it will be less effective.

An anonymous mailer sent this:

A couple of extra things about the T-72's and Russian tanks in general. They are death traps waiting to happen because of the position of the ammunition and fuel.

On an M-1 the main gun rounds are stored in the rear end of the turret with a heavy door between the rounds and the crew. The loader only opens it when he has to pull out a round to load. Otherwise the rounds kept sealed off from them. If the magazine were to explode there are 'blowout' panels on the top of the turret that will vent the force of the blast up and away from the crew. The fuel is positioned as to be a low threat as well. There is also halon fire extinguishers that will flood the crew compartment at the first hint of fire. All of this was tested during the trials. Including setting off a full ammo load to see if the test dummies would survive. They did!

On a T-72 the ammunition is placed in and around the crew compartment. One hit just about _anywhere_ and the whole tank goes up. And for long distance travel large fuel drums are attached to the rear deck of the tank. Somehow I doubt those are armored..

Sergeant Schultz sez:

The accuracy of the M1 series is more unbelievable once you have fired them and worked on them than it is before you get near them. Usually with things like this, the more frame of reference you have the less impressed you become. The opposite was true for me- the more I fired the weapon system and the more I knew about it, the more amazed I am at the machine. I truly fell deeply in love with my tank.

Everything I've heard indicates that the guys who designed that firing system were really on the ball.

Several people emphasized the basic design philosophy behind Soviet tanks was that once a real shooting war started (with NATO, usually, because the USSR thought of that as the biggest threat and designed most of its weapons for that theater) that tanks were going to die in droves, and the only way they could win was to have so many tanks that we'd run out of antitank ammunition first. Since the tanks weren't going to last in combat anyway, there was little point in making them reliable. It was better to have lots of tanks than fewer good ones.

I agree that this was the Soviet philosophy, and to some extent they were making a virtue of necessity. They weren't actually capable industrially of making tanks (and aircraft and pretty much anything else) at the kind of quality and reliability levels that we did. At their best, their engineers were the equals of ours, but their manufacturing was distinctly substandard in nearly every way.

And I also think that this basic philosophy is flawed, because if the tanks wear out fast, then it means you can't afford to use them heavily in peace time to train their crews. If the Soviet Union had given their tankers the amount of in-cab experience we routinely gave ours, they'd have used up a large part of their tank output each year as replacements. As a result, not only were their tanks distinctly inferior in most regards, but the crews were virtually untrained, and would not have had the edge in combat which might have made it possible for them to win even against superior equipment. (Quality soldiers and training can go a very long way to nullify differences in materiel.)

About three people wrote to say that the first sabot rounds were developed by the British at the end of World War II. I knew when I wrote that description that the sabot was not invented at that time; it was more a matter of taking and adapting an obscure and little used munition and making it into the standard antitank round as a response to widespread adoption of laminated armor. And the addition of fins to the penetrator, plus the use of more modern guns with larger calibers and higher muzzle velocities, did make a big difference.

Putting together pieces from several different readers, it turns out that HESH (HEP) most benefits from the use of rifling in the gun. David writes:

The thing with HESH projectiles is that you pretty much NEED a rifled bore to fire them out of. One thing rifling does is that since the projectile is spinning, tiny imperfections in the projectile (mars on the outside and casting imperfections in the filler)