Work hardened brass???

D

Dr Killdeer

New member
How many firings can I get from annealed brass before it becomes brittle or work hardened? Is there a rule of thumb to follow? I shoot Norma brass in a 7mm Rem. Mag with medium loads, not near max. If I have to anneal the brass again, so be it, but the question is WHEN????
 
Belted mags can be pretty hard on brass, even with medium loads. If you're neck sizing and the brass has the same number of reloads on it, I'd say every 3 or so. If you're fl sizing I wouldn't hesitate to do it every firing, or every other at least.

I also have a 7 mag and use norma brass. It's loaded pretty hot and I noticed accuracy problems with brass with between 4-6 reloads before I annealed them. My problem also was that I had random numbers of reloads on the brass. I only get about 6 before the pockets are starting to get flogged out and start getting gas leakage around the primer at 7 or 8.

Sent from my SM-N920V using Tapatalk
 
Variables make it pretty impossible to generalize. I can tell you that Norma's manual says they test reloading life of their brass by sampling production, and that if it can't be loaded and fired 10 times without annealing or any other special steps, they use that as a failing grade.

The belted magnums can be tricky. If you load them at pressures that expand the primer pockets a lot, then that will determine life. Any time you expand primer pockets too loose in fewer than 5 rounds, that should be considered a high pressure sign. The other thing with belted magnums is the way standard sizing dies work often over-resizes them by setting their shoulders back farther than necessary. This also makes the need for trimming more frequent. You can try the Larry Willis collet device (though he is retiring and they won't be available for long, if you want one). I would try to get away with just not setting the shoulder back more than a couple thousandths, same as with a case that headspaces on the neck instead of on the belt. Except for the primer pocket, that will extend life.

The variables are several. If your chamber has a wider neck than the next guy's you will be working the brass more on resizing than he is, if you use the same sizing die. All standard sizing dies over-resize necks and then expand them out again with the expander, working it twice. That is done so the thinnest brass the standards allow will still get resized. But you can buy one of the several brands of bushing die and select a bushing that only resizes your necks just as much as is actually needed to hold the bullets well and then not expand them at all. That adds to life.

How far can this go? Board member Hummer70 says he has one .308 case that has been reloaded 150 times. I'm sure he has annealed it numerous times. Because they put so much effort into finding and elaborately prepping cases that are as near perfect as they can get, and then don't do any more sizing in any direction than is absolutely necessary, benchrest shooters report 50 reloads being not uncommon. But these guys have custom undersized chamber necks to accommodate them doing outside neck turning and still only having half a thousandth to a thousandth expansion clearance so the case doesn't expand much at the neck.

I would expect 20 rounds before necks start splitting can be done with a normal chamber if you are minimally resizing. I would want to anneal before necks start splitting, personally. If you anneal properly (don't overdo the temperature), Norma's requirement of 10 reloads without annealing is probably a reasonable expectation. You might go 20 but lose some cases and, besides, bullet pull is changing with neck hardening. I want it more even than that.

If you overheat the necks during annealing, that weakens the brass, and people doing that report having to anneal every three to five load cycles to avoid neck splitting.
 
Reloading 7mm Remington over the years, my primer pockets get loose long before I have any neck issues with Max loads. I usually get 4-6 with WW Brass.
 
Unclenick hit on exactly what I've found through the years.

Common dies WAY undersize (crunch) the neck down, then drag an expander ball back through them to open up for the bullet install.

The lower end dies are made to resize EVERY CASE EVER MADE FOR THAT CALIBER,
And resize all case materials, and cases have been made of Zinc, copper, brass, bronze, tin, even steel...

About all of us are using cases made from 'Cartridge Brass' or 'High Zinc Content' brass,
About 30% Zinc & 70% copper, so we don't need a die that will resize steel or whatever...

For single rifle hunting & target ammo, (sizing dies for a specific firearm),
I often hone out the die body at the neck, so it doesn't unessaraly overwork the brass.
This is as smiple as an ACCURATE measuring tool, a wooden dowel rod, some lapping compound, a drill motor & some sand paper (sand paper to make the wooden dowel rod fit snugly into the die body).

What I suggest is taking the decapping rod/expander out of your die,
Size a few brass (sample) and see how small the hole in the neck actually gets.
Adjust the die acordingly...

As for annealing, too many variables.
The purpose of case annealing is NOT particularly case life,
Case life is a benifit.

The purpose of annealing is consistancy, each time you anneal you are 'Resetting' the brass to a base line 'Hardness' (or softness, how ever you look at it).

With .223 & .308 brass in my own testing, case life is greatly extended annealing every two or three firings.
My test brass usually got dinged up or primer pockets loosened up before the necks failed.
5.56 mil brass went from 7-10 loadings before cracks to 25-35+ loadings before so many of the brass fired through auto loaders became unserviceable for other reasons, enough to make the sample batches small enough not to gain accurate information.

Similar results with 7.62x51 Milbrass through bolt rifles,
Somewhere around the 25-35 loadings primer pocket issues culled most of the sample batches,
While non-annealed brass often didn't last 10-15 loadings.
 
OK guys, I think I have a better perspective now. Norma brass is pretty consistent. On 20 pieces of new unfired Norma brass I only had to outside turn the necks on 11 of them to get them to within a half of a thousandth. I use the Forster bushing bump die in my Forster press to recess the shoulder 2 thousandths on the fire formed brass and the small expander ball to open the necks. I only resize the neck about two thirds of the way, leaving about 1/3 of it fire formed and I reduce bullet run-out to one thousandth. I'm roughly five thousandths of the lands and the 160 grain Nosler Accu Bond pills are giving me sub MOA. I'm a happy camper, but after all the preparation and range time, if the necks come unglued early it would be a big set back. Thanks for the input guys. I appreciate hearing the voice of experience to help me get things right.
 
I would shoot for 5 firing and anneal.

that is from a lot of reading.

Some do each time (target shooters)
 
I use Norma brass and RP brass in .300 win mag. In my hunting rifle, when I first started reloading, I never annealed the brass. I had 200 pieces of RP brass to start with. I shot about 200 rounds per year out of it pushing a 180 Grain Accubond 3050 fps. With 79-80 gr of H1000. This was a hot-ish load.
When resizing this RP brass I FL sized it until the base touched the die using RCBS FL dies. About 20/200 necks cracked on the 6th firing. About 80 or so cracked on the 7th firing. I discarded the rest after that because I figured they would all crack on the 8th load.

I am now much more experienced and am taking better care of my brass in my .300 wm. I use Redding competition shell holders where I can adjust the shoulder setback in 0.002" increments, I am annealing after every single firing, before resizing.

I don't know about the 7mag but my .300wm cases grow from a factory new shoulder to base of 2.2555 - 2.2715....That is a growth of 0.016" in a Shilen Select Match barrel/chamber headspaced to within 0.0020" of minimum SAAMI.

That would be a whole lot of brass being moved if sized it back down to where it was and case life would no doubt suffer. Norma brass ain't cheap. So what I am doing now is using the Redding shell holders so that I set my dies up just like before and screw them down until the shell holder touches the die well before camming over, and using the Redding "6 set 0.012 die I'm setting the shoulder back about 0.0035".

I may still need to use a collet die someday to push the webbing back in but I expect this brass will last at least 10 loads or more. Norma brass seems to be thicker than RP or win.
 
Over the years in my reloading during Resizing. I have developed kind of a sense in knowing when its time to anneal. Annealing isn't a procedure that needs to be done after a half dozen firings. Its a gradual hardening of brass that happens over time. Be advised if annealing is done wrong its very possible you have reduced your brass's longevity substanchially. Such poor annealing's produce shoulder to neck separation. Soon after a brass's poor annealing job.
 
I agree with doing annealing wrong causing neck/shoulder seperation.
Overheating which causes mono-chrystaline condition is a real issue.
If you anneal for 'Color' change, it's going to happen.
You simply MUST use a fairly accurate way to determine temp and correct as needed.

It's a multi prong approach a lot of times,
My cases that cracked early turned out to be an oversized chamber neck combined with a die that overly compressed the neck during sizing.
By correcting both, the brass lived a lot longer...

This was a bench rifle in .300 Weatherby mag, notorious for being hard on brass to begin with,
I re-cut the chamber with a reasonable neck diameter, and honed the die out to keep over compression of the brass from happening.
In between the re-chamber & die honing I found a little relief, but not as much as I expected.

Turns out the heat from firing was allowing the case to expand without undue hardening, while cold resizing was putting a lot more stress into the case via compression lines in the brass.
At the time, I didn't have a way to quantify grain structure movement, years later it became clear why honing the die gave me increased case life more than the re-chamber did.

Annealing was the step I was missing, annealing made the largest difference in case life by far, and gave me a 'Base Line' for fired cases,
No more tracking how may times each case had been fired.
Once fired a couple of times and annealed, the cases were back to 'Zero' or 'Base Line' and all shot the same again.

Bench rifle cases get a tremendous amount of time invested in them, so anything to prolong life is a gift...
I screwed up annealing seven ways from Sunday when I started.
Nothing out there from actual metallurgists, just the 'Old Wives Tales',
Most are still quoted on any annealing thread, even though most all are inaccurate or just plain wrong.

I started with a candle, then kerosine lamp.
Hard to go wrong with that method since the heat source isn't WAY too hot, but it's time consuming.

Then open gas flame, then 'Vortex' (oxygen introduced) or 'Jet' gas flame.
Quite easy to overheat the case with a jet gas torch.
The dumbest thing I did was wait until the case 'Glowed' or annealed for 'Color',
A guaranteed overheated case...

Once I got out of the military and could own things that didn't have to fit into a duffle bag, I started with pyrometers & thermochromatic paint which helped with consistancy a bunch!
Studying brass was a lot easier once the internet came along, every metallurgical book was easier to find, and I'd been through the old wives tales that produced random results at best...

Take it for what it's worth,
For lonjevity, anneal every few loadings, for consistancy anneal every loading.
Annealing every loading gives you that base line each & every time.
If you are serious, you will wind up with a quick way to anneal consistantly so it's not a 4 alarm event to do...
 
I never got into annealing. I reload on the low side 308 cal. I bench rest only REM 700 , I full length size every time to .001 case headspace. My brass can go as many as 25 reloads. Could it be chamber size that determines brass life ?
 
You must log in or register to reply here.
Back
Top