For our Denali trip last month, I checked in (2) 55-60 lb large duffels full of gear (ice axes, crampons, ice screws, snow pickets, stove, etc.) into Delta's system with no problem other than a verbal "no-no, your bags are overweight" from the checked baggage worker. My friend was charged an additional $25 for having an overweight bag (the limit for Delta is 2 bags of a max weight of 50 lbs without an additional fee). In the past I have also never had any problems checking climbing gear into airlines.
All airlines are different, but I wouldn't worry about transporting ANY climbing gear besides used fuel bottles. They would likely set off the automated baggage scanners which in turn would cause your duffel of gear to be completely taken a part and scrutinized, and who knows how it would arrive... Your best bet is to either ship the bottles to your destination, or just buy them when you get there.
Be safe & have a blast on your Rainier trip!