Proper expander diameter

[triggerjerk]

Have been satisfied with expanders in sizing dies for decades, I finally encountered my first discernible (by me anyway) problem:

600 cases into a batch of 2600 (and 2), the button pulls off inside a case. I cut case open and retrieve button, which won't reinstall on stem due to damaged threads. Grab an assembly off another die, and made the mistake of measuring. Old .2215+ and new .2225. More curiosity killing this cat: anyone know range within which the button should measure? Thx...

[markm]

No idea. I'd have guessed 223 to allow for spring back. If it were me, I'd ditch the button and get a dedicated expander die that sized on the down stroke. It's an added step but reduces trimming and runout GREATLY.

[triggerjerk]

Sound advice and have thought about the change, but turning necks back in the day leaves me worried about seating bullets in ovals. No real runout probs with a button (as visually measured while rolling on a plate....) as I lube necks and work ram carefully. Wouldn't be able to resist trimming, regardless.... Thing is I don't crimp. Measure, chamber, remeasure comparison of uncrimped vs Lee crimped showed uncrimp simply growing a thou or 2. Crimped got longer or shorter a thou or 2 for greater seating depth variation after chambering. Go figure. Am worried about losing a thou of neck tension.... Note that none of this probably matters with my equipment and skill level, but....

[markm]

No real runout probs with a button (as visually measured while rolling on a plate....) as I lube necks and work ram carefully.

I have the runout gauge, and switching to the expander/mandrel type die helped a lot. It's still not perfectly concentric, but much improved.

Wouldn't be able to resist trimming, regardless.... Thing is I don't crimp. Measure, chamber, remeasure comparison of uncrimped vs Lee crimped showed uncrimp simply growing a thou or 2. Crimped got longer or shorter a thou or 2 for greater seating depth variation after chambering. Go figure. Am worried about losing a thou of neck tension.... Note that none of this probably matters with my equipment and skill level, but....

I still trim all my .223 too. It's just that you have to trim MUCH less. And I have no lack of neck tension (by feel) with the expander die method.

[triggerjerk]

Aaaggghhhh! Was under stress (on throne) with my last reply. Was hung up in darkness of old bolt gun days when I couldn't afford bushing dies, etc.... Still weirds me out about alignment of expander with expander dies as I quit using rcbs neck dies because runout was awful due to clearances failing to align case as it entered die (my take, anyway as fl sized cases "appeared" much straighter....). Since you say you definitely measured improvement, product recommends? Lyman?Sinclair? Other?

[markm]

Let me clarify my process. I don't EVER use bushing dies. They didn't work for me.

For .223, I run a Dillon Carbide sizing die with the expander ball removed. This eliminates the pulling action on the neck during the upstroke of the press arm. This however leave the neck sized down too much. So I run the brass on the RCBS neck expander die .224" to get the neck back to where it has neck tension, but not too much where it's shaving jacket material. I set my expander die to where the mandrel "free floats" a little bit... not crazy loose, but the nut is just barely tensioned.

After this I tumble off lube and trim in the Giraud.

(I've always been curios if the mandrel has worn down at all because I run thousands and thousands of cases through it. I don't notice any tighter necks, but I'd think it would have worn thinner a little by now)

[triggerjerk]

Was gonna ask mandrel dia. So, .224? A quick read (dunno where) suggested AR folks were going tight as .222 (or 3) to avoid crimping.... Do you lube inside necks or crimp? Crimping worries me also as my trim length often varies to accommodate shortest cases, and therefore doesn't always leave case mouth aligned with cannelure, if one is present. I usually just load an avg. ten thou less than max oal. For one of the guns, I'll experiment with seating depth because I think I have found it can have good effect even if you are waaay off the leade..... And I, too wonder about my button having shrunk after maybe 8,000 trips through the neck.....

Thanks for the input....

[markm]

My RCBS die is part number 39803. It's nominal size is .224, but the actual mandrel could be smaller.

I never lube the inner necks since I don't need to with the die. But I can see it being very helpful if the expander ball is used (to limit neck stretch)

I definitely crimp with the LEE Factory Crimp Die. If you read Lee's description, you'll see that the die is ideal for long necks. The claim it to eliminate the need for trimming. I use it because in my process, it shrinks groups 3/4 MOA. Maybe because I don't anneal.

[triggerjerk]

My biggest challenge at first was that cases were too short for my Lee Factory die to crimp well or even at all. Test was with sufficiently long, unannealed cases. Didn't get back to annealing until relatively recently. Should I get an expander die, I reckon I'll revisit crimping....

[markm]

This is stuff that just worked for my process. People achieve success doing almost the exact opposite of me too. With the LEE FCD, it doesn't matter how long your case is. If it's too short, it won't hit the brass at all. If it's long, it just crimps more of the neck.

Since I don't anneal, it appears to equalize my neck tensions to some extent. That's the only thing I can think of that would result in such dramatic accuracy improvement. I tested it expecting the "no crimp" ammo to shoot a little better, but found the opposite to be true.