My Green River Rifle Works 1 1/8" across the flats .69 barrel was proofed in 1989, I think the year was. I'd accidently loaded a double powder charge while chronographing loads at the range above the jail where I worked. Since the normal charge was 165gr. 2f, the proof charge was 330gr., with a single 480gr. ball. Although the recoil lifted me up off the seat I was perched on, the velocity recorded at 1,770fps was only 220fps higher than what my normal charge provided for that load. Since that time, this barrel has seen a least 2,000 shots fired with the normal 165gr. load, in total satisfaction.