having barrel built for the 180g berger and 190g matrix. spoke with matrix and said 8 twist might be a little tight. 8.5 is about as tight as he would go. has heard some problems with bullets 190g if spun up to hard. safer in the 8.5 twist. so i will have a barrel built for this application. berger 180vld say 9 twist so anything close should get me in the ball park. 8.5 twist and 29" barrel in a 7 RUM an defensive edge brake. My brake arrived this weekend, sweet! waitin on parts.