Down here Alemite, McNaught and Lincoln have a Loader pump that goes on a 5 gal pail of grease. You just push the bleeder nozzle of the gun into the loader and pump the handle.....no more screwing around with bloody cartridges and grease at near half the price of cartridges. In most guns you need to reverse the piston or shift an O-ring to switch from cartridge to bulk.
The Alemite Loader pump comes with adaptor nozzles to fit Lincoln.
The Loader pump is the ducks guts cause you don't really need to carry around cartridges that get busted and damaged. Every time I'm at the yard wondering what stuff I need to do or organise I just put the gun on the pump and give it a top up. I'd say there is substantially less waste than cartridges although for the last load in the bottom of the drum you need to suck it up the old fashioned way.
On an older gun, if the sealing on the piston is not good you just leave the gun with an empty cartridge in it and re-fill from the loader pump without changing anything....the cartridge acts as a sleeve....and lasts for awhile.
We actually did the cost comparo today....20 litre (5gal drum) costs A$130 and equals 42 cartridges at almost A$6 a pop...or $240....and the Alemite Loader pump costs just under A$200.....so two 5 gal drums and you are in-front....not to mention the convienience.....thats all in Aussie Dollars.....which, the Aud by the end of next week should be worth about $3 US