Via Theo Spark.

I’ll let Esli explain what the Muzzle Reference System is, and how it works.

It’s interesting in the age of hypervelocity kinetic penetrators and HEAT rounds, the Brits chose to go with a rifled 120mm main gun for their Challenger II Main Battle Tank. High rotational speeds are not desirable for either type of round. I’m curious what the thought process was behind that decision.

13 thoughts on “MRS”

  1. This is an interesting picture, but there is something wrong with it, like perspective. This is not the place to be when this old girl decides to express herself. If you stay in place and she expresses herself, you’re going to have a nasty ringing in the ears, if you have any.

    1. More likely to be utter silence. Perhaps permanently.

      I read a cute story about Patton in Torch. His gear had been loaded in a boat and he was held up loading and launching for some reason. The Cruiser he was on had to fire its main guns and the concussion blew out the bottom of his boat, dumping his gear in the drink. He had just had his valet get his pistols out of the boat. Imagine what a 120mm main gun would do to your ear drums standing that close.

  2. Thanks for the technical requirement….
    A 17-foot long thin metal gun tube is subtly effected by temperature changes. For example, friction created by sabot rounds leaving at incredible velocity, cold rain falling on the tube, etc. These have the effect of bending the gun tube because of heat or cold and metallic expansion/contraction. So, the army put the MRS on the end of the barrel. When you boresight a tank, you align the end of the barrel with the target, and you refer your daylight, thermal, and aux sights to the same spot. Then you align the MRS reticle with the same spot. (You do this by actually making the Gunner’s Primary Sight look at the MRS instead of your target.) Now, when your barrel bends because of German snow falling on it, you can realign your three sites (daylight, thermal and aux) with the barrel by realigning them with the MRS. You fire ten rounds and the barrel heats up and the bend changes, you can realign it all by doing another “MRS Update.” Confusing, but just one more component of an incredibly complicated but lethal fire control system.

  3. Not only was she a fire-fighter (after her 71L days), but she has been subject to many a story from me…

    1. They also hit their targets just a wee bit less often, and at considerably less range… And don’t even mention the “old tank’s” 105mm thing; that’s almost closer to a Bradley’s main weapons system…
      As for me, give me an MRS any day.

    2. Actually, the Ord Board did an assessment of gun wear, weather, and other factors when testing the M4 Shermans in WWII. I’ll have to find that PDF in my stash. Yes, even the old 75mm short guns suffered “droop.” However in their assessment, at the expected combat range (less than 1000 yards) the droop did not appreciably effect accuracy.

      I am reminded that in the field, Sherman gunners often aimed at the lower mantlet of Panthers, to ricochet rounds into the weak upper hull plates… and at ranges of about 1000 yards!

    3. MRS was on the horizon when I got out. The ability to “update” things was something we just didn’t have. Of course, on the M-60 the barrel wasn’t even shrouded. We were still back in Armor stone age, so to speak.

  4. QM: Thermal shroud is another nice feature on a tank’s main gun. Helps keep the barrel at a more uniform temperature.
    Brad: the old M2s might be good at BOT, but let me tell you, with the LRF on new Brads, even my tanker self can hit with 25mm pretty quickly. It literally provides first-round hit capability, even though you still fire a sensing round.

    1. Old school 25mm was almost always a first round hit….

      with APDS-T (or rather, TPDS-T)

      HEI-T/TP-T…. well those were a good deal more sensitive to range estimation errors.

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