Brass Bounce Back

[deadduck357]

In industry it is called spring back.
If you size the brass slowly let it dwell about 4 seconds at max stroke of the ram. Then retract about 1/2" and turn 120 degrees. Size again with another 4 seconds dwell. Repeat by retracting and turning again. Size again with another dwell. With enough sizing cycles and dwell eventually the brass gets pushed far enough it cannot spring back. If your brass acts strange give it a little anneal.
Check every case as it comes out of the die with a bump gage. By checking every case as you size it you will spot cases that vary due to variations in your technique. Speed of sizing strokes, number of sizing strokes, dwell time at top of strokes, amount of case sizing lube, hardness of the brass and other variables all can affect the shoulder position because they affect how far the brass pushes into the die.
You may or may not spot these variations with a stripped bolt. However you can easily see variations down to .001 with a bump gage.

"Spring-back" - got it. What's a bump gauge?

 

[Dusty Stevens]

"Spring-back" - got it. What's a bump gauge?

Some way to measure your shoulder bump- one of those comparator things that goes on your caliper or in a pinch a pistol case that the mouth fits on the shoulder somewhere about halfway. Then measure the shoulder setback with your calipers

 

[jepp2]

I was trying to bump the should back and ended up chasing it all over the place just moving the die an 1/8 of a turn would make my measurement go all over the place

WOW! 1/8 turn is 0.009" shoulder movement

 

[deadduck357]

This topic is on that mysterious wildcat with forming dies and all that jazz hes never told us about so who knows how far that brass has moved.

Soon.

 

[deadduck357]

A lot of great advice here, will be implementing these procedures from now on. Thanks to all the above posters.