I am sure that this has been asked several times, so pardon the repetition. But can someone provide me with a drawing or a list of the difference in the parts between AR15 and M4? I presume that the hammer, safety lever, trigger, disconnector and bolt carrier would differ. Are there other differences and if so, what are they? Pictures or a chart would be fabulous. 
are you asking the difference in size? or full-auto vs semi-auto?
m4 is a 14.5" full-auto carbine. ar15 is a 20" semi-auto rifle.
The main difference is the barrel and itâs related parts and the buttstock and itâs related parts.
Everything in the middle is the same taking into account flat top and fixed carry handle models.
This is assuming you mean the semi auto versions compared to each other.
I am well aware and know that there are differences as to the full auto and semi auto, as well as the barrel size between the M4 and AR15. I am asking for a technical explanation. I am interested in understanding the technical differences as they relate to difference in the parts (not in size or function). Maybe a better question is what is not interchangeable between the two? Thanks all 
planning to take apart a Colt M4A1?
all the parts are interchangeable, except for some of the FCG if your AR lower has a shelf or block.
some other variance might be hammer and trigger pins if you have a Colt âbig holeâ lower. that would also negate the use of much of the FCG.
another difference is M4 feedramps that might make barrel swaps more problematic depending on what parts you want to swap and what parts are on the AR15.
this is all pretty minor stuff. AR15s, M16s and M4s are pretty much the same thing.
my guess is youâre wondering about the specifics between full auto and semi auto, as these are the only differences. full auto requires an autosear and autosear hook on the hammer to function, and a receiver milled for such. your selector is also going to be different. you have to have a FA BCG. as i recall, the trigger and disconnector are the same FA or SA while 3-round burst requires different trig and disconnect, as well as a sprocket gear thingy that disconnects after 3 shots. all other components of the weapons are interchangeable and identical.
Actually the disonnector in an auto gun is different than semi auto. The auto disconnector has a tail on it that contacts the selector lever. On a semi auto gun the tail is chopped off because the selector lever does not have the groove in it. I hope that made sense. Anyways- they are different.
indeed- forgot that little important detail. otherwise the disconnector would catch after every round.
Thanks for these impressive answers!!!