PVS-4 focus grabby- frustrated

[M40_A1]

Upon reassembling my PVS-4, the objective focus ring becomes grabby (tight and not smooth) once the internal o-ring becomes compressed.
I noticed a white lubricant when I first received the scope, which I assume was lithium grease, so that is what I reapplied after having cleaned the threads as best I could.
Looking at the manual, silicon grease is mentioned for lubricating the o-rings, but no other lubrication is mentioned for the focus ring threads. Are these supposed to run dry? I'm wondering if the grease is actually causing the problem if those threads are not designed to be lubricated. Thanks for any first-hand advice.

 

[compasscall]

For butter smooth operation and to conform to the OEM and NVESD, use Krytox 240AZ. The only semi-official alternative would be Dow 33 but I'd pick up a tube of 240AZ, it's the only lubricant I use for NV systems. Some use automotive dielectric silicon or food grade silicon, not recommended since it migrates quite readily. Definitely remove the lithium grease, better to use migration prone silicon than lithium. As with the PVS-4, 240AZ is to be used for all lubricated o-rings/preformed packing of 14's, ANVIS etc...

 

[M40_A1]

Thank you for the reply and recommendation. However, seeing that I am not subsidized with taxpayer money there's no way I can justify government contract pricing. $150+ per ounce is unreasonable for grease. I will check out Dow 33. Any other suggestions are welcome. I'm still wondering if the objective focus ring is really supposed to be run dry, as per what I deduce from the manual.
I did, in fact, try silicone grease and it effectively solved the binding problem, but the result was exactly as you said, it migrates pretty badly.

 

[compasscall]

Definitely greased, per the TM.

Correction, per the PVS-4 TM, the silicon grease is DC-33:
"Bulk materials required are as follows:
a. Compound, silicone, DC-33 or equivalent."

The TM for 18's, 15's, 6's and 9's all list Krytox 240AZ as the grease, I use it on all systems as the default, the TM for the PVS-4, TVS-5 and PVS-5 goggles list DC-33.