Was talking with a guy at work about AR's and he mentioned wanting a BFA. I told him I thought there was a difference, but I may be wrong. I remember reading that the red BFA's are for rifles and yellow are for carbines. What is the difference between the 2 or can the be used on either?

Now that I think about it, how loud are blanks?

TIA

The red BFA is the M15A2 and is for the M16A2/A3/A4 rifle system
The Yellow M23  BFA is for the M4/A1 carbine system

The difference is the size of the  orifice that screws in to the barrel that regulates the amount of gas pressure out of the barrel when firing blanks for proper function between the two gas systems. (That's why Uncle Sugar painted them two different colors..)
You will see the occasional Pic showing a Red BFA on a M4 ,etc. Will it work?? maybe, part of the reason Blanks get such a bad rap by soldiers who say they suck/don't work in there weapons etc. (Knowledge can be a wonderful thing )

Blanks are not very loud at all when compared to the actual live rounds. They sound like a "pop".

So it is just the bore size in the shaft that is different. Thanks for the info.

the one on the right is a red one painted black