Wear.

This is coolbert:

As extracted from the web site of "Bayou Renaissance Man" original story thanks to "Strategy Page".

"Are Russian tanks in Ukraine wearing out their cannon?"

 From bayourenaissanceman.blogspot.com/  | February 2, 2023.

"Strategy Page suggests their barrels may be wearing out."

Russian main-battle tanks now being used primarily much as an assault gun [often referred to as assault artillery] would have been during the Second World 'War.

Valuable armor too susceptible to anti-tank missile fire now relegated to a support role.

"Russia responded . . . by using their remaining tanks only for direct-fire artillery support for Russian troops. This meant using HE (high-explosive) shells that explode when they hit something, usually the ground, and create many high-speed metal fragments that will wound or kill troops and damage structures and unarmored vehicles ... Using 125mm HE shells fired by tanks seemed to be a practical solution. It was, but there were unwanted side-effects."

[. . .]

"Russian tanks in Ukraine appear to have used about 100,000 of these shells and in doing so discovered another problem. These shells caused barrel wear on the 125mm tank gun liners. These liners are common in tank guns and tube artillery. It’s cheaper to replace a worn-out liner than to replace the entire barrel and attached loading mechanism. Tube artillery barrel liners are good for 5,000 to 6,000 shells fired. On Russian tanks the liner wears out after about a thousand shells are fired. Most of the Russian tanks in Ukraine used for firing HE shells found that their barrels already had a lot of wear on them and heavy use of HE increased liner wear to the point where all shells (anti-tank or HE) were much less accurate."

Consider within context the observations of the Soviet defector Suvorov that Soviet/Russian 125 mm gun:

"from the very first look, we all liked the 125 mm gun. It was the most powerful gun in the world and no tank  had ever had anything like it before. Because of its amazing initial velocity, its shells could tear away the turrets of tank-targets and hurl them a distance of about ten meters [thirty-three feet], [a tank turret weighs eight or even twelve tons]."

"But now, upon closer acquaintance, our delight with the T-64's had begun gradually to fade . . . the gun [was] . . . smooth-bored . . . and this immediately adversely affected it accuracy. In fact, it was an all-powerful gun, which always missed the target."

"SOVIET/RUSSIAN  125 MM GUN UNLESS SOME MAJOR CHANGES UNABLE TO HIT THE TARGET TO BEGIN WITH AND EVEN LESS SO NOW!!

coolbert.