I have read lots of people complain that the KV-1S is ahistoric, and should not get any larger gun than 76 mm, citing that the only KV with such a gun was the KV-85 (when questioned on the difference between a KV-1S and a KV-85, they fall silent). To clear up any difficulties some people may have with nomenclature, here are some choice bits from the archives.

CAMD RF 38-11355-1377, page 195, fragment

“To arm new “IS” and modernized KV-1S tanks, four 85 mm “S-31″ guns were received, and one “D-5″ gun, designed and produced by factory #9.
The “S-31″ gun has a recoil length of 540 mm, and a large, non-compact mount, which makes it difficult to install in a tank.
The “D-5″ gun has a recoil length of 300 mm, and a compact mount, with a relatively low line of loading. The ballistic qualities of both guns are the same.
Aside from the specified characteristics, the “D-5″ can also be converted to a 122 mm caliber by swapping the barrel and breech.”

And, of course, here is an oldie but a goodie:

CAMD RF 38-11369-106 page 56, fragment

“Installing a 122 mm “S-41″ howitzer on the KV-1S will make a weight difference of _____ compared to the KV-1S with a 76.2 mm ZIS-5 gun (43.5 tons), and will be equivalent to _____ tons.
All specifics of installing an 85 mm gun in the KV-1S and IS tanks are applicable to the changes in the turret and fighting compartment that come with installing a 122 mm howitzer (refer to the TsAKB project “S-31″).”

Hopefully that clears up any confusion as to what KV had what kind of gun in it.