es/sd--again

[cmillard]

by switching to a FL neck sizing die, followed up with an expander mandrel, do you think that will solve some of my es/sd problems so i dont have to switch to a different powder--using tac now. currently, i am running new brass through a sinclair expander mandrel, then lightly cleaning up the necks, followed by FL sizing with a redding FL die with decap/expander. do you think that fl decap/expander could be causing inconsistent neck tension leading to poor es/sd?

thanks

 

[GermanS1]

Inconsistent neck tension can be a factor in ES/SD variance, but correct neck tension is just as important. Your proposed process will probably result in fairly light neck tension. Light tension may be right for your combination - or it might not be. If the ES/SD figures don't improve, or get worse, don't assume it's the process, it might be the setting. That's where bushing dies and turned necks help - very consistent neck tension that can be calibrated to the load.

 

[spclark]

It could be, but with new brass the expander > sizing could be work-hardening your brass somewhat. I've gone over to annealing even brand new cases before any other operations just to take them to some kind of known state of temper. This is with two, different 6mm cartridges and my .308. I use a bronze bore brush to clean the insides of my necks too, running in a drill press, just prior to priming & loading stages.

If everything else works out right I get SD's at 10 or under with .002' neck tension,or a bit less). I aim for less in the bolt gun cartridges, higher in loads for my space guns.

ES's can vary quite a bit but I attribute that mostly to low sample counts more than any other single factor. Generally a good grouping load will still be around +/- 20 fps single-digit SD's.