MIG shielding gas: rule of thumb?

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Searched, but didn't see relevant hits.The MIG calculators I've seen provide a starting point for MIG settings like wirespeed and voltage, but don't give a shielding gas recommendation. Is there a rule of thumb to start with when dialing in settings?
Reply:Reference #1:  http://www.lincolnelectric.com/asset...ture/C4200.pdf.  Read and digest cover to cover.Reference #2:  http://weldingweb.com/vbb/showthread.php...ng+gases+ztfab , specifically post #6 .... courtesy of ZTFab.  Outstanding document covering GMAW shielding gases for each transfer mode (short-circuit, globular transfer, axially spray).Last edited by ManoKai; 12-15-2013 at 10:14 AM."Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi
Reply:That's an excellent reference, Manokai, thanks.To actually >answer< the rule of thumb question, the c4200 Lincoln guide says"The rate of flow for short-circuiting transfer with either CO2 or a mixed shielding gas is usually 25 - 30 cfh, (12-17 L/min). For globular transfer or axial spray transfer, the flow rate is nominally set at 35 - 50 cfh (17 - 21 L/min). Special procedures designed to meet the requirements for electrode diameters greater than 1/16” (1.6 mm) will require a higher rate of flow. Helium, because of its lower density, requires a higher flow rate than those indicated above."
Reply:Check.  Let the puddle/bead characteristics and emitted sound while welding be your guide for fine tuning the flow.  A baseline setup of 30 CFH (short circuit) and 40 CFH (axial spray) works well.  Similaryly, laying down dual/outer shield [FCAW-G] will require you to up the iron between 40-50 CFH.  Good luck!"Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi