All barrels were Remington 7mm magnum takeoffs that were shortened, threaded and rechambered. First one was removed due to poor grouping. It was so long ago, before I took copious notes and didn't know anything about properly cleaning a rifle. Second barrel was removed with 1200 plus rounds through it. There were other reasons for removing barrel #2. I knew the reamer that my gunsmith used was not very good and had dimensions that didn't suit my needs.Also I acquired a used lathe and began doing my own chamber jobs. Last year I ordered a reamer from PT&G that had a neck that required I turn the poor quality Winchester brass AND a very short throat so I could have a 168 VLD engage the lands AND fit the 3.1" magazine. OAL is 3.050".
I would say a custom barrel should last longer than those rough Rem barrels and get at least 2500-3000 rounds if it were a hunting rifle. I read where some F class shooter got almost much and those guys shoot many in a row.