Probably the magazine is not latched in properly. I don't have a 77-44 but I do have a couple of other rotary mag rifles. Have you looked at the latch mechanism carefully? Those parts can sometimes come loose and come apart. I have had to repair the latch mechanism on mine a couple of times.
Ive replaced plunger, latch and ,spring two times. Ill replace the trigger guard next if that won't work ill replace the stock. tnx for ur input. Farrell