[RainyEyes]

How are these mags retaining gas if they don't have o-rings inside the fill valve?

Again, how are you installing them? These are o-rings inside the magazine... Not the outside.

For pistols the best grease is white lithium grease for the metal parts or another silicone based alternative. You gan generally get away with lithium grease not eating away at the plastic parts and it's generally inert for most parts.