The original idea came out of the Pacific theater. Springfield Armory had gotten a request for M1 Garand's with short barrels for use in thick jungle. A short barrel was so much easier to carry in dense jungle cover. Some were made in theater and tried. But when SA made then up for testing they found that a round fired not only lit up the area in bright sun light but the noise of the burning gasses coming out of an 18 inch barrel was tremendous. So other then a few experimental rifles that were made the project was dropped as not being worth the effort. Jump ahead to the late 60's The likes of Fed Ordnance and a couple of others who had their own receivers,(not always of good quality.) but only had surplus barrels that had been cut by the government at the muzzle and the idea of Tanker Garand's came about. They not only made them in 30-06 but in .308 too. The Tanker Garand was never a real deal, just a marketing idea of a sales force out in California.