Big Bore, About 2 years ago, I had my gunsmith set back rechamber 2 barrels, and had mixed success.
After about 1600 shots as a .224 Clark, the Shilen 25.25 inch barrel had about .250 inches of throat erosion, velocity was down about 100 fps, and accuracy had slipped to around 0.75 moa. After being set back and rechambered to the 22/250 AI, the barrel ended up at about 24.5 inches, and I have since put another 450 shots through this barrel, and it is routinely shooting sub 0.5 moa groups. This rechamber clearly has been a success.
After about 1500 shots as a .17/222 mag imp, the Shilen 25.25 inch barrel had throat erosion of about .200 inches, and velocity was down 100 fps. Initially accuracy in this rifle was around 0.5 moa, but after lending it to my brother in law for 12 months, it came back badly fouled, and accuracy from then was almost non existant. After being set back and rechambered, the accuracy is still about the same, and has defied all my attempts to get it to shoot. Clearly this rechamber was not a success, but obviously a worn throat was not the only problem in that barrel prior to rechambering. My gunsmith did not have a borescope but said the barrel was far from pristine prior to rechambering.
Hope the above may be of some help. Brian.
