I have a conversation going on another site where someone is declaring that the early carbine RE's are eqivalent to the present day commercial RE.
I think that they are different and that the present day commercial was developed by Bushmaster (I believe) when the AR was first being cloned for the civilian market.

I think that the threads were cut on the early tubes and that the buttstock area of the tube was shaved down to what is our current mil-spec OD.
I don't know if the early tubes were forged.
I don't know how long that the early tubes were in service.

I have read that the early tubes failed drop tests and that is when rolled threads came in. Don't know the timeline.
Don't know how early these tests would have taken place.


The guy's argument is that current commercial tubes are nothing new, they were the old mil spec.


Are there any historians here that can school me on these early (perhaps XM177E1 ?) carbine tubes, their construction and their evolution into today's milspec tubes ?

Well here is one point, the original tubes aren't "commercial" or "mil spec", they are A1 tubes for use in the fixed stock and there is only 1 construction and diameter.  I bet originally the prototype carbine stock tube was based off that part, and some degree of failure of the collapse and expansion function gave rise to the two position aluminum stock and later four position fiberlites.  (Which is what I remember being on the Colt AR carbine when I first became aware of them back in the eighties.)    

I know the guys here will point out the original carbine stocks look nothing like the current carbine stocks (607) and those sure look like they would protect and reinforce the stock tube.

You might want to check out the perma links at the top, as I think there is some info there.    
 

The 2 position mil-spec carbine buffer tubes as on the xm177 and later carbines go from the 60's to the early 90's.....The Colt 723/727 and other carbines of the early 90's and probably late 80's had the other two positions milled in by armorers or similar people. I have several 2 position buffer tubes that I got from different people at different times that have the same type of modifications done to the tubes.  The 4 position tubes started on the M4 carbines, I believe, but just A guess.

As noted above the FIRST carbine stocks would have been the 607 stock. the earliest "standard collapsible stock setup" for the M16 would be the 2nd generation in the WHOLE timeline of the M16 development.

here's an archived thread of mine

http://www.ar15.com/archive/topic.html?b=3&f=123&t=606316