I've used the A-tec modular on my 85SS at highly recommend it. The only minor design problem for NZ is the recesssed end which can collect rainwater if you carry the gun muzzle up over your shoulder. I took 2 modules out and its still good sound reduction (7mmm08).
I've gone to a DPT for my 6.5 Grendel and it seems great too. Took off all the removable baffles to minimise weight and length. DPT do sell a special wrench to take apart stubborn suppressors. But if you use a lithium based grease, dismantle and spray with CRC5.56 after each day as they recommend there will be no problem. The white/blue deposits mentioned shed flakes are hard as sand and will jam your threads so perhaps that's why they recommend the CRC to keep them in place. Give the DPT guys a ring and they will help you out.
I would go with the "fire a few shots", spray on penetrating oil and clean off with white spirits then grip it really hard with your bare hands while its still warm. Single men and mechanics have more success with this.