So AMX and Harimau has the same gun?
I don't think so.
Their 105 ammunition are different
AMX-13/105 FL12 has the GIAT CN-105-57 firing HEAT (Officially; there are aftermarket APFS-DS being offered IINM)
Note the "bow tie"-shape double baffle muzzle break on GIAT CN-105-57.
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AMX-13/105 FL12 upgrade (gun swapped) has the GIAT CN-105-G1 firing APFS-DS
Note the FL-12 turret with the round-shape muzzle brake of GIAT CN-105-G1 on the first and second AMX, the third (rear) are still in it's original GIAT CN-105-57.
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AMX-13/105 Retrofit has the same GIAT CN-105-G1 firing APFS-DS
Round-shape muzzle brake of GIAT CN-105-G1.
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Harimau use Cockerill 105mm
Note the different profile of the muzzle brake, fume extractor and the presence of thermal jacket on the barrel.
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Tl;dr, Harimau does not use the same guns as AMX-13, AMX-13/105 has French proprietary 105×528mmR caliber, the L7&Cockerill 105 has NATO standard 105×617mmR caliber.