Question on resizing 300WSM to 7WSM
- Thread starter 220 Swift AI
- Start date
Neck size the 300 down to 7mm, only far enough down the neck that it creates a false shoulder to headspace on. This will leave the bottom ~.050" of the neck 30 caliber. Cases should headspace slightly tight such that you feel just a bit of drag on the bolt handle as you lock the bolt.
Load standard 7WSM loads.
Shoot.
Annealing case neck after fireforming is a good idea.
Another method if you don't want to do it "right" with the false shoulder is to seat bullets LONG, ensuring lots of jam into the rifling, which will keep the case head in contact with the bolt - making sure all brass flow and movement occurs up front at the shoulder. Reduce charge accordingly.
Load standard 7WSM loads.
Shoot.
Annealing case neck after fireforming is a good idea.
Another method if you don't want to do it "right" with the false shoulder is to seat bullets LONG, ensuring lots of jam into the rifling, which will keep the case head in contact with the bolt - making sure all brass flow and movement occurs up front at the shoulder. Reduce charge accordingly.
Last edited:
