.30-06 and .30-06 Sprg. are the same thing. The Springfield came about because the .30-06 was originally developed as a military round and carried the designation of the 1903 Springfield. In 1906 the cartridge was change slightly and became what we know as the .30-06 today. .30 caliber Model of 1906, and keeping the designation of Springfield because of the Springfield Armory where it was developed. (I think- regarding Springfield Armory). .30-06 is just used as a shorter designation for .30-06 Springfield.