Thread: Case lengthening when bump sizing

Originally Posted by -BW-

4. Sizing can happen 2 ways, full length, or neck only. The terminology of 'bump sizing' is somewhat misleading, as it is nothing more than full length sizing but only just enough to bring the shoulder within spec of the rifles chamber, but not all the way down to the shellholder. It seems some people do this with or without the expander ball fitted. Correct me if I'm wrong here but this is as I understand it.

True shoulder bump sizing as it is used in benchrest and target reloading does not use a FL die (unless the neck portion has been reamed out, making it a body die).

What you are describing above (FL die screwed down only far enough to bump the shoulder) would still size a portion of the neck. Measure the neck OD or ID before and after sizing to confirm this.

True bump dies do not touch the neck at all. The diameter of the neck is the same after (shoulder and body) sizing.

My primary concern during reloading is to work the neck as little as possible. Neck tension is the holy grail w.r.t accuracy, and I do everything I can to get consistent neck tension.

What I do is this:
Body die to push the shoulder back (but not touch the neck)
Collet die to size the neck (in as concentric a way as possible)

Or you could combine both operations into one by using a bushing bump die with appropriate bushing to give you the neck tension you require.

Both these methods do not use an expander ball, so the neck is never stretched beyond the fired dimension.