I have been wondering for quite a whije what is the purpose for it.Most MBT or at least many have it.You know what I mean ? it’s the stuff that looks like the asbestos lagging on old steamboiler pipes,& has metal cinch clamps evert couple feet on it.Though I mentioned steam pipe insulation,I can’t imagine that’s what it’s for,hot barrels aren’t particularly a good thing.Especially in the middle east. Thanks ahead, rudedog
It is thermal insulation. Essentially it’s purpose is to reduce differential expansion in the barrel caused by variations in temp from one side to the other, such as a difference which might be caused by wind or rain from one particular direction. A temperature differential from one side of the barrel to the other may result in a slight bending of the barrel, which has an impact on its accuracy.
You may note that the current generation of 120mm guns don’t appear to have the thermal insulation. This is because they incorporate a MRS (Muzzle Reference Sensor) at the end of the gun, which is tracked automatically by optics in the gunner’s sight. Any deviations in the barrel are “reported” to the computer systems and factored into a firing solution.
It’s to prevent “gun tube droop” which Phil describes fairly well. As a tank sits overnight, the barrel cools and in the morning it will be more ridgid. As the day goes on, the tube heats up and begins to droop. Also firing the gun will cause it to heat up and add to the droop.
Phil is incorrect in stating that modern 120mm guns do not have a thermal shroud. They do. Even with a thermal shroud, gun tube droop still occurs. The MRS is used to compensate for the gun tube droop during the day, but is not a substitute for proper daily boresighting.
When the gunner uses the MRS, he manually toggles his reticle to align his sight with the MRS. This will change his aim point. There’s nothing automatic about it. If you’ve ever used a joystick on your computer, the calibration process is similar in concept to using the MRS.
The MRS has been in use since the initial M1 appeared with the 105mm gun. It too had a thermal shroud.
Cheers Rob,
Thanks for the correction.
Thank you,Phil & rob.After you both explaied it,It makes sense. I guess My thougts,That they were for keeping heat in the Barrel isn’t the isissue [ It sorta is indirecly ] But to keep any expansion or barrel droop as you called it,to do it uniformly. Thank’s again guys.Semper fi, rudedog