Having a 338 Lapua built with a Defiance action and a Bartlein 26" Heavy Palma contour with either. 1:10 or 1:9.5 twist. Any suggestions as to which twist rate? Most likely plan on shooting 300 gr. Berger OTM.
9.5 is what I have on my custom build and I lob 285s and 300s down range all the time. Even the 250s have good performance out of there, can't go wrong.
I ran the numbers in JBM when building my 338 to shoot 300SMK's. If I remember correctly all you need is a 12 twist. I went with a 10 twist and am more than happy