Expanding Mandrels

[SDHNTR]

This biggest issue is from mass produced dies designed to size a case to an extreme amount (to cover everything) then run a .001 under button through. This can cause issues around the shoulder neck junction.

I think a button could be employed successfully if you were to control the diameter of the neck being sized, and the button size.

I “mandrel” similar to how a button would in my SAC dies as the brass leaves the die, the difference is I control the neck and mandrel size, and I also start the mandrel process as soon as the brass leaves the neck. I have seen zero difference using this method, besides a little less in the pocket book.

That’s exactly what I do. I use a bushing die with a carbide button and just squeeze enough so that I feel the button barely running back through the neck. I still can’t see what advantage a mandrel would give me. And it’s an extra step.

 

[HuntHarder]

That’s exactly what I do. I use a bushing die with a carbide button and just squeeze enough so that I feel the button barely running back through the neck. I still can’t see what advantage a mandrel would give me. And it’s an extra step.

I am not sure anyone is trying to talk you into it. Mandrels are pretty cheap if you want to experiment for yourself. If you are happy with where you are at, I would not change a thing. Some of us have noticed better spreads using a mandrel. I am not saying you will, but I did. I like to "tinker." It may be in my head, but I also notice a more consistent pressure when seating bullets if I mandrel. I use 21st century FWIW.

 

[Harvey_NW]

That’s exactly what I do. I use a bushing die with a carbide button and just squeeze enough so that I feel the button barely running back through the neck. I still can’t see what advantage a mandrel would give me. And it’s an extra step.

That process might not see any benefit because you're minimizing brass movement and probably aren't dealing with the same amount of springback. My assumption about a mandrel making a difference was in reference to a standard FL sizing die, where there is more movement. I could see running the neck over a mandrel with 100% of the surface area being expanded to the same diameter with a second or two of dwell time providing a more consistent result than just pulling a button through that is only expanding the portion of the neck it's touching while being pulled through.

Bushing dies are also 2x+ the cost, and don't size the entire neck potentially causing a donut.

Although I haven't noticed any issues on target, I'm intrigued. I plan to test it for myself and see if it's worth it.

 

[KyleR1985]

Then IMO opinion you're good using just bushings with no advantage to using mandrels. I use a plain bushing die with no expander ball and no mandrel's. As I said somewhere yesterday or today many LR BR and SR BR competitors would agree and do just that, bushing only no mandrel, no expander balls.

I’m dumb - just want to make sure I understand you here.

I have a Redding type S bushing die. The die I bought is loaded round neck diameter - .002.

You’re saying if I were you, you’d just pull the expander ball off the decapping pin, and full length size the brass with no internal work done to the neck, load and shoot?

 

[KyleR1985]

I just pulled the expander from my Redding type S bushing die, replaced it with the thinner decapping rod holder.

Fired brass neck measures .274”.

Sized 5 cases with .264 bushing and with the expander ball - all .264”.

Sized a case with a .264” bushing in the die, no expander ball. The neck measures .259”.


I pulled the .264” bushing out and measured its ID - .261”. Expander ball OD .240”.

How would not using the expander in this case make more sense than using it? I’d have a lot of neck tension it seems like.

The next step of using a mandrel to set ID makes sense this way. but to forego the expander ball and not use something to expand size of necks, I’d have to go to a bigger bushing. By my dumb math I’d think a .267”

What am I missing here?

 

[BBob]

You’re saying if I were you, you’d just pull the expander ball off the decapping pin, and full length size the brass with no internal work done to the neck, load and shoot?

Absolutely. That’s how I and many others do it. I have never used an expander ball/button in a Redding Type S full size die and this goes back at least 30 years. I have some Neil Jones’s dies that have no way to even put an expander ball on the stem.

I’d have to go to a bigger bushing. By my dumb math I’d think a .267”

What am I missing here?

You’re missing nothing. Use the appropriate sized bushing to get the neck size (aka tension) you want.

Do you have a way to accurately measure the wall thickness of the neck? Calipers will be close but are not exactly the accurate way to do it. Internal wall of neck has a radius, caliper is a flat. Measuring a case neck with a caliper will give a slightly larger measurement than what it actually is.

I’ll add that if using your die as is with the expander button gives you an acceptable accuracy I’d change nothing and carry on as is. If you want to play with neck tension, spend less $$$ and save a step then experiment with bushing size rather than a separate step with a mandrel and mandrel die.

 

[KyleR1985]

Absolutely. That’s how I and many others do it. I have never used an expander ball/button in a Redding Type S full size die and this goes back at least 30 years. I have some Neil Jones’s dies that have no way to even put an expander ball on the stem.

You’re missing nothing. Use the appropriate sized bushing to get the neck size (aka tension) you want.

Do you have a way to accurately measure the wall thickness of the neck? Calipers will be close but are not exactly the accurate way to do it. Internal wall of neck has a radius, caliper is a flat. Measuring a case neck with a caliper will give a slightly larger measurement than what it actually is.

All I have to measure is caliper. I got .012 wall - with caliper.

Loaded virgin case measure .266 - which would indicate .0115 wall.

Hence I bought .264 bushing.


How do I rectify that when I sized case with .264 bushing and no expander, the neck measured .259”?

 

[BBob]

How do I rectify that when I sized case with .264 bushing and no expander, the neck measured .259”?

Not sure how that can be. What does the ID of the bushing measure?

 

[KyleR1985]

Not sure how that can be. What does the ID of the bushing measure?

All the measurements are in that post above. .261”.

My guess is the ID of the sizing die where neck gets shoved through makes it that small?

 

[BBob]

My guess is the ID of the sizing die where neck gets shoved through makes it that small?

The die shouldn’t be that small. The only time I’ve seen that problem in using a Type S die is going up in caliber over what it was originally made for like using a 6BR die for a 30BR. I’d check it though because it wouldn’t be the first time something isn’t what it is supposed to be. I’ll add it’s not uncommon for some bushings to not be exact to size but I’ve not seen one .003” off before.

 

[wapitibob]

I use a neck bushing die to set neck finished dia by stepping down neck bushing dies. Fired neck OD is .318, I neck down with .315, .312, then .309. I then use a body die to bump shoulder and size body.

Common internet belief is that using a bushing only will give you a round neck OD and the excess mtl moves to the ID. Using a mandrel will give you a round ID and move the excess mtl to the neck OD. Checking necks on a CMM will show it doesn't work quite like that; not all excess mtl magically moves to the neck OD when using a mandrel, so I don't use one as a regular step. I do use a turned down 30 caliber button and run it thru brass that has a dinged neck to bring it back to the .318 OD starting dia.

 

[KyleR1985]

The die shouldn’t be that small. The only time I’ve seen that problem in using a Type S die is going up in caliber over what it was originally made for like using a 6BR die for a 30BR. I’d check it though because it wouldn’t be the first time something isn’t what it is supposed to be. I’ll add it’s not uncommon for some bushings to not be exact to size but I’ve not seen one .003” off before.

6 dasher Redding Type S bushing die with .264” bushing.

I measured .261” ID of that .264” bushing with calipers.

I confirmed that, at least relative, it’s correct - by sticking the .264” sized neck(measured with same calipers) into the bushing, after sizing it with the expander installed, with the bushing out of the die…. Or rather, not being able to.


This all seems normal to me - the brass is compressed to below .264 and springs back to that number once out of the die.


But I’m ignorant when it comes to this stuff.

I do like simple, and no nonsense - which is why im pressing here - I want you to be right so I can eliminate unnecessary time and variables thay don’t make me and my gun better.

 

[BBob]

I want you to be right so I can eliminate unnecessary time and variables thay don’t make me and my gun better.

I’m not going to claim to be “right” but I and many others including lots of SR BR and LR BR winning competitors do not use a mandrel and solely use a simple full length bushing die without an expander button.

 

[KyleR1985]

I’m not going to claim to be “right” but I and many others including lots of SR BR and LR BR winning competitors do not use a mandrel and solely use a simple full length bushing die without an expander button.

I’ll size one in a minute no bushing installed. See if it’s the die.

If not - is my .264” bushing wrong? When I size a case with the expander installed it comes out at .264”.

 

[KyleR1985]

I’m not going to claim to be “right” but I and many others including lots of SR BR and LR BR winning competitors do not use a mandrel and solely use a simple full length bushing die without an expander button.

Sized one with a .267” bushing, and no expander. Came out .264”.

Surely my calipers can’t be off.

Checks zero….

Off .002” ….. haha


.264” bushing makes .263” - close enough for an imprecise tool.

Back to your regularly scheduled programming.


Thanks for the back and forth, I’ll load up some same loads with and without expander and report back in my thread on the 6dasher Howa mini

 

[Lawnboi]

I’m not going to claim to be “right” but I and many others including lots of SR BR and LR BR winning competitors do not use a mandrel and solely use a simple full length bushing die without an expander button.

How many of those same guys are neck turning their brass?

I know a few guys successfully doing the same, not putting anything through the inside of the neck. They are all running premium components and reamers made to their spec.

 

[BBob]

How many of those same guys are neck turning their brass?

A trend has been growing in using unturned necks sized with a bushing only. Bart Sauter is one that has won a bunch doing just that. I believe Alex Wheeler has done some testing as well. I want to say he’s had some success but I don’t recall all of what he’s said about it. FWIW Wheeler is a no internal neck lube (nylon brush only), no mandrel, bushing die guy. I’m doing it (no neck turn) because neck turning for a field rifle is a waste of time. I did it for years though because it had to be better right?

Oh! I would say though that most BR and other competitor's are turning necks and using non-SAAMI chambers. The trend there though has been going to more and more increased clearance in both neck and throat.