>"The majority of the gas comes spurting right back up along the "needle" of the Brunton Fuel Tool."
Okay, well that torpedos my plans for that adapter I just ordered. Can't ever have too many adapters around the house, but maybe I should impose on some of my EAA (experimental aircraft association) buddies for some shop time. They have some serious shops! And use a lathe to make an adapter from each fuel type to 1/8" pipe thread. Then I can match anything to anything and really get in trouble.
Have you tried chilling the receiving canister first? I never saw it anywhere, but it just made sense to me and I've always done it for propane-propane transfers. And keeping the donor cartridge at room temp or a little above.
Of course I have 3 freezers (kitchen freeze at 10-15F for ready reserve stuff, in-house chest freezer at -5F for the next month of stuff, and the deep freeze at -15F to keep the sockeye fillets as fresh as possible for as long as possible) plus it's been -25F outside for too long this week so I can play with fuel canisters without Kristin noticing.
Back to your Brunton refiller: So that little stem is just a bit too small in diameter? Like by a few coats of paint? Hint. Hint. Or a thin film of 2-part epoxy painted on?