Go to your local matches and see if you can try out a few different ones. I'm sure many would be happy to help you out. Once you figure it out, as stated before, get something from one of the well known smiths, either new or used. 38super, 38supercomp and 9 major are all viable calibers for Open but I went with 9major initially because of the cost since I have a source of brass but the big advantage is not having to pick up my brass after I shoot. The constant bending down and getting up were taking a toll on me during the match especially in the warmer months and was affecting my performance. The brass is always scooped up by someone else anyway.