I couldn't give you exact time, but with ten major contractors barrels were always in short supply. The war production board created a barrel exchange program to help alleviate any shortages or production stoppages due to lack of barrels. With the major contractors, Marlin Firearms, along with Buffalo Firearms were also contracted to produce barrels for the pool. There were about 50 sub-contractors for most of the other parts... even receivers. Some of the majors only made the receiver and sub-contracted the rest out. That's why it's tough, along with all the armory rebuilds after WW-2 and Korea, to find a WW-2 carbine as they left the factory. If you get a chance you might look up the website www.uscarbinecal30.com, they used to be m1 carbine inc., guess the changed their title. They have some pretty good info along with some of the other carbine forums. Hope this helps. -Lloyd BEERCHUG1for the knowledgeable Carbine buff, when did Marlin get into the M1 Carbine business? What parts did they supply other than barrels?