Recently while reading old posts I saw some folks posting about feeding problems related to short barrels, specifically I believe 10.5" and shorter... Various posters mentioned using different parts to alter the gas system (or other parts of the platform) in order to make the shorter barrels function properly.

Well, assuming one wants to use standard, bone-stock parts, what is the shortest barrel length (for .223) that can be assumed will function flawlessly?  11.5"

Thanks.

You may want to go to the Full Auto section for answers. They have plenty of tacked threads regarding C3 items.

You are pretty much on to it.  11.5 barrels purchased from barrrel makers (meaning they have the correct gas port diameter work well with most ammo.  My Bushy 11.5 will from 40gr to 75 gr ammo just fine.  When you go down to 10.5 inch, the problems start.  Then people adjust gas port diameter, buffer weight, and buffer spring tension to fine tune thhe weapon.

Also, check the M-16 section here for n more specifics.