Thread: Case lengthening when bump sizing

Before I launch into this , I'd first like to apologise to @knightshade for derailing his thread with this topic. Sorry .

I'd also like to say that this thread is in no way meant to be preachy or argumentative , ust for discussion .I'll try to get the tone right .

Okay, so this seems to be a relatively common phenomena and the question has appeared a few times of recent on the Stalking Directory forum over here in the UK . The question usually arising after f/l resized fired formed brass won't chamber . I think the question is becoming more regular as more people seem to be trying to just push the shoulder back a couple of thou" .

So here's my and other people on the SD's understanding .

A full length sizing die sizes in the following order , outside neck diameter, body/web , shoulder then finally inside neck diameter . The lengthening occurs when the body has started to be size before the shoulder engages the die, think squeezing a ball or balloon , it gets thinner but longer . Now anyone who thinks the body doesn't get sized would be mistaken , if that were the case no one would ever encounter a stuck case due to lack of lube .

To give some weight to this , I stumbled on this after a rebarrel and purchase of new Hornady dies . I use Redding competition shellholders , they're easy to setup, give consistent results and I'm a bit lazy.

I started with the 0.010 " shellholder and the cases became difficult to chamber and measurement with the comparator saw an increase in length of about 0.002" . The 0.008" saw no measurable difference and chambered fine . The 0.006" resulted in a shoulder setback of 0.001-0.002" shoulder set back , which was my target . These figures are from memory as I didn't think I'd ever need them . I should have perhaps taken note of the effect on the case length by measuring head to neck .



I should add that I had been made aware of this but wasn't looking for it , I was just setting up a die and spring back was unlikely as I anneal .

This isn't an attempt to teach others to suck eggs , more a question of other people's thoughts and observations?

Regards all