Re: Neck Tension
Okay, a good question but I hate to write long posts.
There really isn't any grip difference in "bullet tension" after necks are about 1 thou under size, the rest is just permanetly stretched during seating. The increased resistance we feel when seating in smaller necks is only the added effort required to expand the neck with the bullet, it's not real "bullet tension/grip" at all and that increased seating effort does have a "con" I'll touch on below. And don't take my word for this, you need to do an experiment to prove what I say to yourself.
Size two cases, expanding one neck as you normally do, then remove the expander plug and size the other without expanding. Mike the outside of each loaded neck about mid point, marking the location of mike contact so you can return to the same point later. Record the numbers.
Seat a bullet in each so shank contact with the neck runs to the shoulder (using a boat tail will make seating easier in the smaller neck). Notice the effort required to seat in both cases, it should be easy to tell which one was normally expanded and that incorrectly suggests it's gripped tighter. Mike the necks again, same point as before, and write that diameter on your note sheet.
Pull the bullets, measure and record the neck diameters a third time.
No matter how much smaller your unexpanded neck was before seating, both will be virtually the same, within the limits of your ability to measure them, and they will only be about 1 thou smaller than the loaded diameter. With this you will see and have proven there is no significant grip difference in a sized fit smaller than the final difference you measure, the rest simply stretches the brass past its elastic limits.
Smaller necks - "high tension" - seating harms accuracy by producing increased bullet run-out. Driving a bullet into a too small neck forces it to be the final expander and that increased resistance tends to tilt the bullets as they enter, making them enter off-axis and increases run-out for absolutely no benefit in grip.
Bottom line, there is no advantage to making neck inside diameters smaller than 1 to 1.5 thou and there are some very real disadvantages to going smaller than that.
Last edited by boomtube; 09-06-2010 at 09:02 AM.