How hard should a former be to work with cartridge brass?

Trboatworks · Dec 27, 2022

I am turning some formers to expand the necks on cartridge brass.
What material and hardness is required to stand up to this task?

I would like to use 17-4 as I have the material on hand but will purchase anything required.
This is the type of former I am making- it is an expander which is pushing a thin wall tube out a few thousands.
This former has an OD of .353" pushing a .345" ID of .011" wall out to size:

Thanks all

M. Moore · Jan 2, 2023

I don’t know the answer but I am sure others will want to know how many you need to process.

farmersamm · Jan 2, 2023

I saw this a bit ago, and forgot about it. I've never considered the Rockwell on a die. I shoot a lot of pistol, and do quite a bit of reloading.

Anyways................ From https://www.brownells.com/reloading...-dies/precision-resizing-dies-prod144254.aspx

I never knew they used 12L14 on other dies, seems soft, but what do I know. Machines like a dream though.

I suppose, not really knowing any better, that in order to harden the material they're using for their "improved" dies, you'd have to grind it true after hardening. Dunno. I don't do anything that requires heat treatment.

FamilyTradition · Jan 2, 2023

According to this page: https://alloys.copper.org/alloy/C26000 , cartridge brass at its hardest is around 90 on Rockwell B scale. I imagine after manufacturing and firing a bullet that it has been work hardened a fair bit.

I am going to guess that if you can get your die somewhere on the C scale for Rockwell, it will work fine. As farmersamm found, some dies run all the way up to 80 on the Rockwell C. You may be able to get away with softer, it just won't last as long.

As for the heat treatment part of it, something like you are making, you may be able to get away without having to finish grind if you use a case hardening process like nitriding (I don't know if this process also works with stainless steels but I imagine 17-4 has its equivalent, I have not worked much with heat treat of 17-4). I have seen nitriding done on parts that have already been ground to finish size, and we are talking .0005 tolerance or less on these surfaces.

Something I would also check if you had one of the purchased dies, and you haven't done so already, is if there is any draft/clearance on the die, and how much there is. If you turn it dead straight you might get it stuck in the cartridges.

henrya · Jan 2, 2023

Almost any steel will work. I'd go for the best finish over hardness. Your 17-4 will be fine.

MilGunsmith · Jan 3, 2023

Lubing the brass is normal and that stops any appreciable wear. Some pistol dies are made with a carbide insert or expander button to avoid the lube process Dirty brass is what wears out dies, not the brass as it is softer than steel, the dirt is an abrasive.

akajun · Jan 3, 2023

If these are new cases, they'll be clean, however if they are fired, i dont care how much cleaning they will still have microscopic particles of carbon and will abrade.
Ive made a few ball expanders out of 4140, 4130, around 32rc but not for high volume use. After a few hundred rounds you can see scratches but they still work. Id try one of those and get the hardness up if you have the ability.
Most swaging dies are made from s7 from what I can tell, hardened to the 55c range but those use a lot more stress than expanding case mouths.

Having the expander nitrided would probably help too.

henrya · Jan 3, 2023

If you're worried about wear, just make several now with the material you have. You might want some size variants too. But you will probably only need one, if this is just personal use. If it was a part for a commercial line and it would see many millions of cycles then the whole hardening thing comes into play, or more likely you'd use carbide.

Trboatworks · Jan 3, 2023

Thank you all.
Yes my own use so thousands but not tens of thousands.
The 17-4 former I made pictured above scored after a hundred rounds so I need to step up the game a bit.
Brass wet tumbled with the little stainless shards so pretty clean.
I did harden the former after a fashion- the 900 degrees for an hour and air hardening but may have botched it somehow.

henrya · Jan 3, 2023

Dry tumble with some Nu-finish car polish and they will slide through the die slickly.

BOB-OO · Jan 3, 2023

Carbide, extremely well polished.
Everything else S7, M2, M42, CPM10v will produce an order of magnitude less correct parts. Once the form gets ANY brass on it at all its a snowball running downhill. Use a quality stamping lube. The polish is critical-like a mirror. Most people think thin brass should be easy to work with, it's not, watch for heat buildup if your going faster then 50pcs/min. We've been working to get our quantities up between cleaning/sharpening tools and have tried all the materials listed above and more.

Trboatworks · Jan 4, 2023

Thanks for that.
Carbide is not on the table as I cannot make in my modest shop.
This is not a commercial rate process- simple hand press at expected speed and cycle rate for that sort of work.
Maybe a few hundred an hour.
I would just buy these but I am working on obsolete equipment.

I have to take a careful look at the one I have- it may be that I have brass stuck to surface and it is not in fact scored.

Edit- scoring is present.

This is a comparison of a OEM former and the one I made.
The old former has probably seen a ton of work and is fairly uniformity hazed surface from it.
The one I made is headed there.
Acceptable?
Maybe so.

72bwhite · Jan 4, 2023

One shot case lube
and the finish needs to be ground or highly polished
try using A2
the other cheap one to try is mild steel with cherry red
polished up the cherry red is fairly slick.

polish what you have and use some lube. See how it works
I found even on straight wall with carbide dies just a touch of lube makes a big difference
I have had build up of brass on a rcbs expander when doing new brass without lube.

really clean and new brass needs to be lubed inside the

EmanuelGoldstein · Jan 4, 2023

I'd go with 8620 carburized about .050" deep.

The material is cheap and easy to get. Probably someone here has a chunk they'd send you for shipping.

Any old heat treater who can write his name will get you 63 Rc with it, and very little distortion. Your 17-4 will maybe come up to the low fifties but more likely the mid-40 Rc range. For wear resistance, meh.

With a .050" case you can easily polish it to a nice mirror finish and do touchups later without worrying about going through. Nitriding is only a few thou thick.

Easy to machine. You'll have to pay the minimum charge (was $50 at mine) at a heat treater's but that's about the only cost. Don't go hobbyshop and try to do it yourself, case counts.

It's good stuff.

henrya · Jan 5, 2023

If you want it hard:

BROWNELLS SURFACE HARDENING COMPOUND | Brownells

Easy-to-use compound case hardens plain and low carbon alloy steels. Carburizes surfaces quickly to uniform depth while retaining the toughness of the core. ...

www.brownells.com

And you will use this again.

bigjon61 · Jan 5, 2023

Everything we have ever made for reloading equipment for one of the big names in the game has been 12L14 and case hardened.

farmersamm · Jan 5, 2023

bigjon61 said:
Everything we have ever made for reloading equipment for one of the big names in the game has been 12L14 and case hardened.

Do you carburize it?

farmersamm · Jan 5, 2023

henrya said:
If you want it hard:

BROWNELLS SURFACE HARDENING COMPOUND | Brownells

Easy-to-use compound case hardens plain and low carbon alloy steels. Carburizes surfaces quickly to uniform depth while retaining the toughness of the core. ...

www.brownells.com

And you will use this again.

50BMG DUDE · Sunday at 9:33 PM

I made a bunch of tooling for one of the big manufacturers at one time in AZ - Can't say who.

All 12L14 - Carburized .008 case depth min

If I didn't want to screw around having something hardened, use 4140HT, polish it well, use imperial sizing wax.

I resize.50 BMG brass that is headspaced long in a M2HB occasionally. You have to crush the whole case back .010-.030 - using Imperial sizing wax has never gotten a full length case stuck in a sizer yet.

Lube is your friend!

eaglemike · Monday at 12:49 AM

Expander plugs made from 12L14 to size, carburized, then polished to a mirror finish will work well, as noted above. Another old school reloader company did them this way for many years and they would last for hundreds of thousands of rounds. The case is harder than the 17-4, even at H900. The old company I know of used a chemical salt bath that's not able to be used any more in California, other methods will work though.
Tumble the brass with liquid car polish that also has wax in it. I used a very old school car liquid car wax/polish brand name Westley's because that's what I used on the cars back then. Run the tumbler with corncob or walnut with the polish for a bit to get it spread out and absorbed some in the media. This will clean and help lube the process a tiny bit.
Good luck!

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