first time using bushing & expander mandrel - can someone confirm my math?

[Winny94]

First time using an expander mandrel with a bushing die, and Id just like some confirmation on my math before purchasing the bushing(s).
Goal is .002 tension
Loaded case measures .2925
Minus .002 desired tension
Minus .001 spring back
Minus .001 to account for expqnder mandrel
Gives me .2885 so I should order a .288 & a .289 bushing, yes?

Secondarily, using a redding die - are the nitride bushings worth the premium over the stainless?

 

[spife7980]

292-.004= .288 bushing.
.288+.002 from turning arbor =.290 finished sized brass.

 

[Winny94]

292-.004= .288 bushing.
.288+.002 from turning arbor =.290 finished sized brass.

I'm not turning necks, so the .004 measurement I had looks to be right

 

[spife7980]

I'm running the expander mandrel, which expands .001, not the neck turner of .002

Loaded diameter is .292-.264 bullet diameter is .028/2= a neck thickness of .014

From a case thats sized down to .288 and .028 of case neck material your inside neck diameter would be .260. An expander mandrel would open that inside diameter up to .263. .263+.028= .291. The expander mandrel will get you to your goal of .001 neck tension/interference fit. But it will open expand .003 in this scenario, not .001. With a .289 bushing it would expand .002. (I think you probably meant expand to .001 under, not expands .001)

Since you know that you are wanting only .001 difference then the .289 bushing would be what I would do to minimize brass work, .288 for future flexibility. Or both if you can spare the scratch.

I havent found much evidence of any actual spring back but Ive always anneal each firing since I made the move to mandrel dies, maybe once its hardened after a few cycles it will be more of an issue.

 

[Winny94]

Loaded diameter is .292-.264 bullet diameter is .028/2= a neck thickness of .014

From a case thats sized down to .288 and .028 of case neck material your inside neck diameter would be .260. An expander mandrel would open that inside diameter up to .263. .263+.028= .291. The expander mandrel will get you to your goal of .001 neck tension/interference fit. But it will open expand .003 in this scenario, not .001. With a .289 bushing it would expand .002. (I think you probably meant expand to .001 under, not expands .001)

Since you know that you are wanting only .001 difference then the .289 bushing would be what I would do to minimize brass work, .288 for future flexibility. Or both if you can spare the scratch.

I havent found much evidence of any actual spring back but Ive always anneal each firing since I made the move to mandrel dies, maybe once its hardened after a few cycles it will be more of an issue.

Thanks. I think we're on the same page, you are just more thoroughly explaining it. I'll start with .289