ok ive done the google yahoo search and forum search and i have come up empty does any one know what type of steel m2 50. cal barrels are? low carbon high carbon?

4140 usually with stellite chambers and throats (usually)  some are Cr lined..some are not...

Barrels are meant to be tough, not hard. What era is the barrel from? They have been made by several contractors for over 70 years....

If the barrel still has rifling I would sell it, and use the cash to go buy some known material. M2Hb barrels are always in demand-- I used to work for a machine gun dealer. 

As I remember Harold Johnson of Cooper's Landing AK, used a M2 50 cal. barrel off of a fighter plane to make his 50 Alaskan. The throat was shot out so h cut it off  and mounted the rest on an 1886 Winchester.

Turns out those barrels are not as tough as you'd think, 5500 rounds of sustained fire will melt the rifling right out of them.  Weird, huh?

One time while I was in Viet Nam we tried to zero in an M-2 .50 cal on an area where we suspected hostile night time traffic.  We couldn't observe any impacts even though the tripod and traversing and elevating gear were tight and the sights were right on target with the appropriate range set.  I got some tracers and when we fired them they went down range in a very pretty expanding spiral.  The barrel looked fine but it had been shot out and the lands and grooves had eroded together and it was something well over .50 caliber because of wear.  The bullets just rode down the barrel on one side or another and left the muzzel in an increasing spriral trajectory.  We gave up on our long range plan and just used it for short range defense across the helipad.  That's when I learned that an eroded barrel can look like it still has decent lands and grooves.

GNM

(late of 1.C/1/12 Cav 1Cav Div (airmobile), RVN 1970-71)