30.06 Cases Fracturing

International SOF · October 21, 2009, 08:13 PM

I am using a 30-06 Ackley Improved. This of course necessitates reloading as this it is a wildcat cartridge. I am using 168 grain HPBT bullets and the recommended powder charge for this combination. I have noticed that my cases appear to be fracturing when I fire them. This fracture appears circumferentially approximately 0.5-1.0 cm from the base of the cartridge. It occurs in maybe 20% of the rounds I am firing, and in most cases does not completely encircile or separate the cartridge into two pieces (although in one case I was able to pull the two pieces apart by hand.) I have been reloading standard rounds for years for my .45 ACP, .308 FN-FAL, and other weapons, and have never seen this happen before. I am VERY accurate with powder loading so I do not believe this is an effect caused by over charging. Does anyone have exprience with such an effect, causes, solutions??? Obviously I am discarding said fractured cases when discovered.

Slamfire · October 21, 2009, 08:34 PM

I would need to see pictures to be sure, but it reads as if you are having case head separations.

If this is true, it is likely that you are pushing the shoulder too far back on your cases.

Or, if you are fire forming them, the cases are separating due to excessive case stretch.

On a nice clean case, and a nice clean chamber, the front of the case expands and holds the case in place. Then, as pressure increases, the base of the cartridge is stretched to the bolt face. If the stretch is too much, you get case head separations.

I was worried about this when I acquired a 35 Whelen. The previous owner claimed he had case head separations. He did not set up his sizing dies with cartridge head space gages.

I necked up 30-06 brass. But even then the shoulder distance was likely to be way off. So I fired the first 100 cases with a light load (pistol bullets), and I lubricated the cases.

Lubricating the cases eliminates case stretch. Lubrication prevents the case neck and shoulders from gripping the chamber walls. The lubricated case slides to the bolt face and the shoulders fold out to the contours of the chamber. The end result is no measurable case head stretching.

After fireforming I then resized the cases ensuring that I had just enough shoulder setback to close the bolt without any resistance.

I checked the shoulder setback with a Wilson cartridge headspace gage. I do not know if they make one in 30-06 Ack Improved, but a cartridge headspace gage is one of the most important tools needed for safe, proper resizing of bottleneck cartridges.

To date, I have not had the case head separations the original owner experienced.

wncchester · October 21, 2009, 08:36 PM

"I have noticed that my cases appear to be fracturing when I fire them."

It's called a "head seperation" and hard to not notice isn't it?

It's caused by excess head space, the case is driven forward by the firing pin and primer explosion, powder pressure locks the fore part against the chamber walls. Increasing pressure eventually pushes the head back until it contacts the bolt face and stops. The area you see the seperation is where the stretch occurs. If the stretch is small there is little effect, if it's too much it pulls apart as you are experiencing. It is potentiall hazardous, I'm a bit surprised you haven't had a worse result already.

There are several ways to control the required fireforming you need to do but it would take more than I care to write to explain. You need to get a book on wildcats and study it.

reloader28 · October 21, 2009, 09:52 PM

I have a 243 with a long headspace and was having the same problem. I just raised my FL sizer die up an 1/8 or 3/16 and started neck sizing them. It fixed the problem, my cases last a LONG time, I very rarly have to trim and it shrunk my group size from 3/4 to 3/8 inch. I do this with most of my guns and it works really well. Youre only sizing about half the neck and nothing else on most calibers.

**Unclenick** · October 21, 2009, 11:46 PM

Welcome to the forum.

More specifically, you have what is called incipient case head separation, meaning the separation begins, but is incomplete. Good thing, since a separated head leaves the rest of the case inside, and if it doesn't shake out, you have to get a large enough brush on a cleaning rod and get it out with that. If the separation was caused by very high pressure, the remaining case portion can stick and require a special extractor tool to remove.

The above suggestions about case forming with low pressure loads are good. I hadn't thought about a thin film of lube, but it may offer some insurance. Basically, though, cases loaded below about 30,000 psi don't develop enough pressure to stick to the chamber walls hard enough to stretch, even without lube. Something in the 10,000 PSI range works well for forming, and the case will back up in the chamber, and blow the shoulder forward rather than stretching the case where the head thins out into the wall. In your gun, you can get some of the Hornady or Speer 100 grain half jacket plinker bullets or whatever equivalent you can get where you are, and put it over about 8 to 9 grains of Unique or Hodgdon Universal for your forming shots. Lead bullet loads are also fine.

Afterward, also follow the suggestion only to resize as far as you really need to for reliable feeding. The number usually given for a bolt gun is to measure the head-to-shoulder length after firing and set your sizing die up to make it about 0.002" shorter after sizing. You need a case comparator on a caliper to measure this.

If you don't need to feed the rounds from a magazine, consider neck sizing to maximize case life.

International SOF · October 26, 2009, 08:45 PM

Yes the cases I am using were simply fire formed from commercial 30.06 rounds. So the pressure during forming may be excessive. Independently someone suggested buying new brass and fireforming that, consistent with the advice you are giving here. I will definately go that route in future, applying lubrication as suggested. Will also work on the resizing as well.

Thanks for all the feedback on this one. I now have a number of things to work on. Much appreciated!!

October 21, 2009, 08:13 PM	#1
International SOF Junior Member Join Date: October 21, 2009 Posts: 2	30.06 Cases Fracturing I am using a 30-06 Ackley Improved. This of course necessitates reloading as this it is a wildcat cartridge. I am using 168 grain HPBT bullets and the recommended powder charge for this combination. I have noticed that my cases appear to be fracturing when I fire them. This fracture appears circumferentially approximately 0.5-1.0 cm from the base of the cartridge. It occurs in maybe 20% of the rounds I am firing, and in most cases does not completely encircile or separate the cartridge into two pieces (although in one case I was able to pull the two pieces apart by hand.) I have been reloading standard rounds for years for my .45 ACP, .308 FN-FAL, and other weapons, and have never seen this happen before. I am VERY accurate with powder loading so I do not believe this is an effect caused by over charging. Does anyone have exprience with such an effect, causes, solutions??? Obviously I am discarding said fractured cases when discovered.

October 21, 2009, 08:34 PM	#2
Slamfire Senior Member Join Date: May 27, 2007 Posts: 5,261	I would need to see pictures to be sure, but it reads as if you are having case head separations. If this is true, it is likely that you are pushing the shoulder too far back on your cases. Or, if you are fire forming them, the cases are separating due to excessive case stretch. On a nice clean case, and a nice clean chamber, the front of the case expands and holds the case in place. Then, as pressure increases, the base of the cartridge is stretched to the bolt face. If the stretch is too much, you get case head separations. I was worried about this when I acquired a 35 Whelen. The previous owner claimed he had case head separations. He did not set up his sizing dies with cartridge head space gages. I necked up 30-06 brass. But even then the shoulder distance was likely to be way off. So I fired the first 100 cases with a light load (pistol bullets), and I lubricated the cases. Lubricating the cases eliminates case stretch. Lubrication prevents the case neck and shoulders from gripping the chamber walls. The lubricated case slides to the bolt face and the shoulders fold out to the contours of the chamber. The end result is no measurable case head stretching. After fireforming I then resized the cases ensuring that I had just enough shoulder setback to close the bolt without any resistance. I checked the shoulder setback with a Wilson cartridge headspace gage. I do not know if they make one in 30-06 Ack Improved, but a cartridge headspace gage is one of the most important tools needed for safe, proper resizing of bottleneck cartridges. To date, I have not had the case head separations the original owner experienced. Last edited by Slamfire; October 21, 2009 at 08:40 PM.

October 21, 2009, 11:46 PM	#5
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	Welcome to the forum. More specifically, you have what is called incipient case head separation, meaning the separation begins, but is incomplete. Good thing, since a separated head leaves the rest of the case inside, and if it doesn't shake out, you have to get a large enough brush on a cleaning rod and get it out with that. If the separation was caused by very high pressure, the remaining case portion can stick and require a special extractor tool to remove. The above suggestions about case forming with low pressure loads are good. I hadn't thought about a thin film of lube, but it may offer some insurance. Basically, though, cases loaded below about 30,000 psi don't develop enough pressure to stick to the chamber walls hard enough to stretch, even without lube. Something in the 10,000 PSI range works well for forming, and the case will back up in the chamber, and blow the shoulder forward rather than stretching the case where the head thins out into the wall. In your gun, you can get some of the Hornady or Speer 100 grain half jacket plinker bullets or whatever equivalent you can get where you are, and put it over about 8 to 9 grains of Unique or Hodgdon Universal for your forming shots. Lead bullet loads are also fine. Afterward, also follow the suggestion only to resize as far as you really need to for reliable feeding. The number usually given for a bolt gun is to measure the head-to-shoulder length after firing and set your sizing die up to make it about 0.002" shorter after sizing. You need a case comparator on a caliper to measure this. If you don't need to feed the rounds from a magazine, consider neck sizing to maximize case life. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

October 26, 2009, 08:45 PM	#6
International SOF Junior Member Join Date: October 21, 2009 Posts: 2	Thanks Guys Yes the cases I am using were simply fire formed from commercial 30.06 rounds. So the pressure during forming may be excessive. Independently someone suggested buying new brass and fireforming that, consistent with the advice you are giving here. I will definately go that route in future, applying lubrication as suggested. Will also work on the resizing as well. Thanks for all the feedback on this one. I now have a number of things to work on. Much appreciated!!

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October 21, 2009, 08:36 PM	#3
wncchester Senior Member Join Date: December 1, 2002 Posts: 2,832	"I have noticed that my cases appear to be fracturing when I fire them." It's called a "head seperation" and hard to not notice isn't it? It's caused by excess head space, the case is driven forward by the firing pin and primer explosion, powder pressure locks the fore part against the chamber walls. Increasing pressure eventually pushes the head back until it contacts the bolt face and stops. The area you see the seperation is where the stretch occurs. If the stretch is small there is little effect, if it's too much it pulls apart as you are experiencing. It is potentiall hazardous, I'm a bit surprised you haven't had a worse result already. There are several ways to control the required fireforming you need to do but it would take more than I care to write to explain. You need to get a book on wildcats and study it.

October 21, 2009, 09:52 PM	#4
reloader28 Senior Member Join Date: October 13, 2009 Location: nw wyoming Posts: 1,061	I have a 243 with a long headspace and was having the same problem. I just raised my FL sizer die up an 1/8 or 3/16 and started neck sizing them. It fixed the problem, my cases last a LONG time, I very rarly have to trim and it shrunk my group size from 3/4 to 3/8 inch. I do this with most of my guns and it works really well. Youre only sizing about half the neck and nothing else on most calibers.