It is unclear whether the blow was sufficient enough to break the reservist’s arm and perhaps prevent him from being sent to Ukraine.
As two women inspect the wounded man’s arm, the sledgehammer-wielding friend asks: “What do you mean… I didn’t?”
Another shocking video of apparent draft-dodging shows a man appearing to break his friend’s leg.
The unwilling soldier lies at the bottom of a stairwell with his foot resting on the bottom step.
The friend climbs up towards the top of the staircase then jumps down, landing on the leg-bone and stamping it into the ground.
In the short clip, the wounded man could be seen grimacing in agony as the friend pulled his jumper over his head in apparent shock.
Kremlin officials have warned Russians against deliberately injuring themselves in order to squirm out of Mr Putin’s mobilisation.
But the new trend highlights the desperation among Russians to avoid being sent as part of ill-equipped and trained units to join the Russian president’s invasion forces.
‘Protest is more effective’
Urging Russians to demonstrate against the mobilisation, Andriy Yermak, the head of the Ukrainian president’s office, wrote on the Telegram messaging app: “They mutilate themselves so as not to be mobilised.
“Protest is more effective. But this option is not for slaves.”
Since Mr Putin announced last week that he would call up 300,000 Russian reservists at least a quarter of a million military-aged men have reportedly fled the country.
With many of them leaving via the frontier with Georgia, border officials have imposed restrictions on vehicles arriving from elsewhere in Russia to quash the mass exodus.
Other acts of desperation to avoid the draft include one Russian man setting himself on fire and another shooting a military commander at point-blank range in a muster centre.
British military officials on Thursday said the exodus of those seeking to avoid being called up had threatened Russia with a “brain drain”.
In its daily intelligence update, the Ministry of Defence said: “When combined with those reservists who are being mobilised, the domestic economic impact of reduced availability of labour and the acceleration of ‘brain drain’ is likely to become increasingly significant.”
More men had fled Russia, it added, than were part of the army that initially invaded Ukraine.