If it has factory spec wby freebore you won't find the lands and have enough bullet left in the case neck or won't fit in the mag. Try to seat with the bt at the neck/shoulder junction and start with 67-68grns retumbo or 64-65grns H1000 and work up. You will likely have the best results with retumbo, id also use br2 or fed210m primers to keep the es down, if you must use a magnum primer, use winchester LRM. You will likely get 3050-3100fps but jumping those bullets and your twist rate I'm not so sure your going to get top notch accuracy.