Must admit been subject of some debate and experimentation over the years..

> CO2 can freeze the regulator under heavy use

Few turns of microbore copper wound round a 60W inspection lamp bulb used to be the answer to expensive heated regulators appparently.

>"pub" CO2 bottles

Some `smoothflow` or something , gases have a nitrogen/CO2 mix for smaller bubbles, worth avoiding.

Was one theory about CO2 being `rougher` than argon mixes, was possible lower temperature freezing out more atmospheric moisture into the weld.

Big machines certainly help, being handed torch of an already set up 350A Cebora was a whole lot easier than trying to set up a Migmate 100.

Little bottles main problem is once opened they rarely reseal properley so can cost wrong side of a tenner to make a couple of tacks.

Fabrication welding on the bench with new stock a bit differnt from repair welding of rust to rust in a freezing lane as well ;-)

Wire feed is one thig that sticks in memory as being much steadier on big machines, colleague used to repair machines, Oxford used to make oil-cooled copper cored welders, another world from air cooled aluminium, but another universe price wise as well.