Question: Tank Gun Thermal Sleeves?

Couple of different reasons; one is that it keeps the gun at a more constant temperature and minimizing inaccuracy due to gun tube droop. Secondly it retains the heat signature that can distort thermal sights.

PaPa Peng wrote the following:

Thanks for the answer. There is still the question of overheating. It won't take too many rounds for the gun barrel to become red hot. The tube metal expands, The tube diameter shrinks and that seizes the round (as per overheated machine gun barrel.) What then?

Cool water circulating around the barrel, like from the tank's AC unit.

The shroud helps the gun heat at a constant rate (for example, sun on the topside of the barrel will make it expand faster than the bottom, thus inducing curve and droop). Most modern systems (including the Russians now) have a muzzle reference system which tells the gunsight and fire control computer how far the barrel has warped out of its boresight.
Cookie Sewell

: : Thanks for the answer. There is still the question of overheating. : It won't take too many rounds for the gun barrel to become red hot. : The tube metal expands, The tube diameter shrinks and that seizes the : round (as per overheated machine gun barrel.) What then? : I understand modern gun tubes are made with a process called "hydro swaging". Two telescoping tubes are used, the tube is filled with a fluid, the ends sealed, and the fluid is expanded.
The inner tube expands past its' plastic limit, and remains forever expanded to its current size. The larger outer tube does not expand past its' plastic limit, so it is constantly attempting to squeeze the smaller tube back to its original diameter.
Also, I doubt the tube diameter shrinks. At Waterloo, IIRC, the Kings German Regiment was frantically looking for oversize balls for their muskets at the farmhouse(?) they were attempting to hold. Same story at Rorke's Drift during the Zulu wars. (Actually, I believe the KGR were simply looking for ammo, period).
And, finally, I wonder how much heat a modern smooth bore gun tube absorbes? Without the friction of the rifling, it is probably not as much as a rifled barrel would generate/ absorb.
Bruce

...why would you think a modern gun bore isn't rifled?

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Bruce Because some are not. The 120mm smooth bore gun is used on the Abrams, Leopard 2, Type 90, etc.

If the tube metal expands, then the diameter cannot shrink, it must also expand. That is, if the circumference of a circle increases, the diameter must also.
The only reason a car engine seizes when it overheats too much is that the piston is hotter than the cylinder walls because it does not get cooled as well.

These days there are both out there- smooth bore and rifled bores- depends on the gun.

...ok, "some" I'll buy. All of the medium to large bore guns I've personally encountered have been/are rifled. Up to and including artie bores...I'm not up on the tank world.

That I'll buy...our local Marine Detachment has a heavy aritie shell that has been pierced in-flight by a Phalanx round sitting outside the CO's door...that shell has rifle marks on it. I guess I need to go hang out around some tanks.

Rufus,
Today nearly all 120mm and 125mm tank guns are smoothbores -- the British are the only ones who stand by the rifled gun in that caliber. 105mm are mostly rifled but the French had smoothbores.
Smoothbores work better with APFSDS and HEAT rounds as they do not impart spin, and the fins on the projectiles provide stability. HE- FRAG and normal APDS work better from a rfiled gun.
Cookie Sewell

: : This explanation doesn't quite agree with the observation that the red : hot barrel of a gun causes the bullet or shell to jam in the barrel : (?). : I read a comment about US 105mm crews using replacement barrels faster than was expected. When a team showed up to find out what was going on, they found the 105 crews could fire the gun faster than the 5 rpm "offical" factory max, and as a result, were wearing out the rifling. Apparently, up to 30% of the lands was gone.
It is also possible that, in the case of the Bofors, the crew was attempting to change the barrel. I expect if the tube expands, you will have a hell of a time getting the barrel to rotate to unlock the threads. Not to mention, it can't be pleasant to handle. :-)
Bruce

Yeah...different weapon(s). The only large guns I have any sort of brush with are ship-board or mobile artillery. Of those, I've always/only seen rifling marks on the rounds. Far lower rates of fire too, I'd expect.