The only firm figures I have for Russian synch guns are for the 12.7mm UB, but I have seen some figures quoted for other guns. This extract is from 'Flying Guns – World War 2: Development of Aircraft Guns, Ammunition and Installations 1933-45':
"It is however difficult to find many actual examples of the effects of synchronisation on rate of fire. As already mentioned, the Soviet 12.7 mm UBS fired at 800 rpm instead of 1,050; a reduction of 24%. It also appears that the ShKAS was slowed from 1,800 to 1,300 – 1,500 rpm (17 – 28%) depending on the installation and the ShVAK from 800 to 700 (12.5%)."
Tony Williams: Military gun and ammunition
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