Many questions: How were the originals made? Were they cut down full lenth triangle handguards? Were front and rear stamped metal Delta rings especially made for these?
Can these be made by cutting down triangle type handguards ? What parts would be needed to do this.
I know there is a company making reproductions of these but the quality is not good.
Thanks for your help!

I am not aware that triangular handguards were ever used on issue carbines (XM177, CAR-15, or M4).   I cannot recall ever seeing them on any AR-15's with 16" barrels, either.

I have seen pics. IIRC, there's a company making them. I do'nt have the link, but i'm sure someone will post it in no time.

Apparently, the only triangle carbine HGs were put on a couple of early experimental carbine types built up by Colt when they were first trying to peddle the AR to the government. They were never an issue item, and I doubt any more than a few hundred were ever made, if even that many.

I don't see any way you could modify an A1 rifle set to work as carbine length.  Even if you could cut the rifle set down and get it to fit on a short barrel, without destroying it, the dimensions of width and height would be all wrong.  Apparently someone has made up some in the right dimensions, because I've seen pics of a couple.  To my eye, they look like crap.

Total Silence  home.comcast.net/~luthier4/ has the short carbine triangle handguards.
There's a stamped triangular piece of sheetmetal with a lip at the rear.  The handguards are shortened from the back, with the front part staying the same.

uxb & a few other arfcommers have them on their carbines, uxb even has the early style telestock on his (Colt xm601 style).

home.comcast.net/~luthier4/

I think this is the one.

http://home.comcast.net/~luthier4/images/xm607.jpg

I also found this:

Quoted: Last time I checked they were around $35.00 per set. Hay River Trading Co. P.O. Box 176 Almena WI 54805 715-357-6054

i want one made for my mid-length...

that would be interesting to see