crushing case necks when using expander mandrel to open case neck on a 338SS

[Calvin45]

To build pressure in the case, I pack the case up to the neck with toilet paper over the powder to build pressure. The paper is gone by the time that the pressure would build enough to expand the neck.

I see what you're saying…I think .

Part of me wants to try this for myself just to see what happens, put a .300 win through the .358 Norma die with the decapper expander unit removed just to bump the shoulder back so it chambers and see if the neck expands with a fire forming load

I'm not at home right now but just might do an experiment to verify to a certainty one way or another. Because while it's a nuisance, a primer consumer, and time waster, if it actually does work it might be a good thing for any number of us to know about. Same if it doesn't haha.

 

[scpaul]

Yep, it will waste primers.

 

[Tidesloe]

Have you tried using a vld chamfer tool before you use the expander? You might also try mika dry neck lube.

Another must as a solution

 

[Calvin45]

Yep, it will waste primers.

Probably. I have some very old, very suspect primers that I'd never use in loads for serious work but odds are they still go bang. I have nothing to lose here haha. Unless you've actually done this and can tell me from experience that it can't be done I'm probably gonna give it a whirl for and giggles

 

[scpaul]

No, I never tried to expand the neck with the cream of wheat method. I guess that you might get a little expansion depending on how tight the paper is when it goes through the lands and throat to build the needed pressure.

 

[Tidesloe]

Probably. I have some very old, very suspect primers that I'd never use in loads for serious work but odds are they still go bang. I have nothing to lose here haha. Unless you've actually done this and can tell me from experience that it can't be done I'm probably gonna give it a whirl for and giggles

Probably nothing to loose in that case to try out of curiosity, but not likely to get a lot of expansion I'm guessing. I don't know, just surmising. Let us know how it goes.

 

[Calvin45]

Probably nothing to loose in that case to try out of curiosity, but not likely to get a lot of expansion I'm guessing. I don't know, just surmising. Let us know how it goes.

I will if I get around to it. I'm sure you guys are right and don't doubt you but, when it's a low-stakes experiment like this, I'm one of those curious idiots that likes to verify things for himself

 

[scpaul]

That's how you learn things like using a Lee crimp die to neck 30 down to 7.

 

[Tidesloe]

I will if I get around to it. I'm sure you guys are right and don't doubt you but, when it's a low-stakes experiment like this, I'm one of those curious idiots that likes to verify things for himself

I hear you there. Nothing wrong with that and crazier things have happened, some probably even worked. I've got primers I could burn too at no big loss.

 

[Calvin45]

That's how you learn things like using a Lee crimp die to neck 30 down to 7.

Wouldn't have thought of that haha. But I can see how it would squeeze it down

 

[MAD10]

2 mandrels 30 cal. See the difference between a regular mandrel and a neck expanding mandrel. The expanding mandrel has a very gradual taper, hard to even see in the picture. These are K&M brand.
View attachment 483307

Wow very pronounced … appreciate the photo

 

[timo308]

I had this issue when expanding my 338ss brass. I was using the first run stuff so 30 deg shoulder that still required fireforming. Anyway, I was crushing 1 in about 5 doing the 2 step .308/.338. So I picked up a .32 mandrel from brownells. Just adding that extra step solve my problem.

Ryan

I was about to say that the OP needed to drop an 8 mm mandrel in between that .308 and .338 mandrel. I don't seem to have a lot of luck when I try to go more than 15 to 20 thou. when expanding case necks.I even turned down an old .308 scratched up mandrel to .295 to cover the gap between 7mm to 30 cal.

 

[Mike Matteson]

You are expanding the neck. I would use Imperial Wax instead of powder. I think I would use a brush too. A longer taper mandrel would help. I would increase the sizing in 2 steps if not 3. Go slowly, don't push it down quickly. Lube is your friend as long as you don't put to much on or in it.
Yes you have to clean your cases. That better than loosing them. Good brass is over a $1. ec now.
I am probably will have to, to get top quality brass for my 338WM rifle.

 

[akmtnhnt]

I had this exact same problem with the 338 sherman max. I used the 21st century 7mm to 308 neck up expander, but at the time they did not have the 308->338, and by the looks of it they still don't. I tried using a straight 337 mandrel, crushed cases. I had a buddy with a lathe make me a 308->338 with the same taper as the 21st century ones. Still got a lot of collapsed cases. Of all the things that finally worked was just running the 308 necks through the Hornady FL die with the expander ball in there with all of the cases chamfered and graphite as lube. I'm not sure why an expander ball works better than a much more gradual neck up expander mandrel.