Vigillinus, These barrels have a 1 in 12" twist, and are the same twist in most 375s. I had a set of these barrels a few years ago, and rechambered them to 375 JDJ, and they worked out fine! Now factory ammo is available for the 375 JDJ, and would make into a fine rifle for serious Bear hunting in the North America, as well as a fine cat rifle for Africa!