Daniel,
Green River Forge did not make any barrels. When they were owned by Frank Straight and located in Bellevue, Washington, they used barrels from Sharon Rifle Barrel Co.
If your rifle has a 1:72 twist, it's a Sharon barrel.
Frank Straight sold the business in early 1977, and it was moved to Springfield, OR. Just before this move, Sharon Rifle Barrel Co. went out of business, and the Springfield, OR based Green River Forge started using Green River Rifle Works barrels. Then at the end of 1979, Bill Bandenburg, the Business Manager at GRRW bought Green River Forge and moved the business to Roosevelt, Utah. Confused enough?
Other than having very similar names and both ultimately located in the same town and being linked by Brandenburg, the two companies, GFR and GRRW, were separate entities. GRRW went bankrupt in September 1980--less than a year after Brandenburg bought GFR.
Brandenburg continued to operate GFR in both Roosevelt, Utah and in Fulton, California for a number of years after GRRW went out of business, but he doesn't appear to have built many guns in that period. His business focused on selling apparel, books, and patterns for period clothing.
You can find more history on
Green River Forge here and a full description of the guns they offered.
Phil Meek