3.175 seems a little short. Most loads i see are at 3.250-3.270. The lighter slugs are 3.170, but that is for 90 and 100 grain loads. Try seating them to 3.250 and see how they do. If the bolt closes without force it should work. If it does close with force, the col is too long. If it seems ok, try a few loaded with minimum powder and see how they shoot. If I am mistaken, somebody correct me.