To remove the bolt, raise the bolt handle, then check for an empty chamber.
Pull the trigger, and while holding the trigger back, withdraw the bolt out to the rear.
It may just need a good cleaning, followed by proper lubrication.
The M-43 is basically a re-inforced rimfire Model 69A on steriods, i.e. it has two locking lugs ILO one, is larger/heavier, and has a different magazine catch.
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