It's shockingly easy to have galling seize up threaded connections in titanium and/or aluminum. The presence of silicone grease does not cause it, but it does nothing to prevent it because it provides no useful lubrication properties for a metal-on-metal interface. However, the typical anti-seize compounds aren't advisable for pressure vessels because they have combustible hydrocarbon bases. That's where one of the PFPE / PTFE greases like Krytox or Ultimox come in.
Tungsten disulfide is another effective lubricant, and it's what I use because it's both inexpensive and serves multiple purposes in the airgunner's toolbox. For this purpose I keep some in an eyedrop bottle, the powder mixed with alcohol 50/50 by volume. Super easy to apply to threads this way. The alcohol wicks rapidly to carry the powder into the threads and then quickly evaporates. And like molybdenum disulfide, it also makes a great dry lubricant for burnishing into hammers and bolts/cocking mechanisms and the surfaces they ride on. The advantage over wet lubricants being it doesn't attract and trap dust and blowing debris, and for the hammer specifically it won't affect the strike at varying temperatures the way a wet lube may do because of changing viscosity.
FWIW this is the stuff I bought. I think it was a little cheaper on ebay at the time, and there very well may be generic sources where you could get more of it for a similar price but an ounce of this stuff will probably lubricate 50 airguns. It goes a long way.
