FX Impact M3 bottles getting really hard to screw on

Anyone else have the issue of air bottles getting really tight to screw on/off? To the point where I start to worry about the amount of torque I'm putting on the bottle itself. Mind, I'm still screwing the on with bare hands but especially if you can't get a good grip, for example when screwing on a 480cc bottle with a saber bipod rail extender, it takes all the grip strength I have to get it on or off. The higher the pressure in the bottle, the bigger the issue.

I've tried cleaning the threads both on the gun and inside the bottle, tried lubricating the threads with a light coat of silicone grease (I've since learned that that is not a good for threads under pressure, and it was cleaned off using alcohol), tried lubing the threads with a small application of copper grease, but nothing seems to work. Anyone else has this problem or knows a solution?
 
Yes the silicone grease is your evil culprit causing the problem. I have no explanation as to why but that stuff is a seize compound on metal to metal surfaces.
The silicone has long since been removed but the issue is still there. Also, the issue started before I ever touched it with silicone grease, which is why I applied it in the first place.
 
I have always used Krytox for my Bottle threads and O-rings...
I have the 300 bar bottle..... So...
Push the bottle into the gun as you screw on the bottle when you hear the bottle valve opening...
Same thing when removing the bottle. Apply some force on the bottle into the gun as you Start removing the bottle..Until you hear the pressure release..