It would seem that keeping magazines loaded for long periods would weaken the spring and possibly cause misfires. Is their a "rule of thumb" about downloading magazines periodically to avoid such issues?
I just noticed that the elusive magazine for the model 85/86 can be found on gunbroker. The seller is offering 2, each for $125.00. These magazines are impossible to find, so if you own an 85 or 86, this might be your chance.