how to tell if a case is safe?

jambrdly · May 12, 2010, 08:42 PM

Hello:

I'm fairly to new to reloading and I was just wondering if someone could tell me what the visual or measurable signs of an unsafe case are? Also, if there is a website that perhaps shows examples? I have read about "cratered primers" for example but I have no idea what visually distinguishes a cratered primer from a normal fired primer.

mrawesome22 · May 12, 2010, 08:44 PM

You need a reloading manual.

Try a search for "over pressure" or "excessive pressure".

dmazur · May 12, 2010, 10:05 PM

Brass can stretch, and some reloaders look at changes in case length as an indication of overpressure. Since this is affected by work-hardening and brass alloy, it isn't reliable.

Similarly, the primer can "flatten" and fill the gap between the primer and primer cup. It can even make the cup larger in diameter. This doesn't always occur with overpressure.

The primer can "crater", or show brass flow up around the depression created by the firing pin. This can also be caused by excessive clearance between the firing pin and firing pin hole in the bolt, so it doesn't necessarily indicate overpressure.

The head can show ejector marks. This can also be caused by the presence of lube in the chamber, so, again, this isn't a reliable indicator.

With the variation in barrel performance, even a chronograph reading that shows you are "in range" for a given load won't prove whether you are experiencing overpressure or not.

Almost everyone would agree that if you see all the signs listed above, you are probably overpressure. However, no single visible (or velocity) cue is proof.

An instrumented barrel, using RSI transducers and software, is probably the best indicator. Around $600, I believe -

http://www.shootingsoftware.com/pressure.htm

Anything else is guessing. Perhaps educated guessing, but still guessing.

briandg · May 12, 2010, 10:16 PM

there are NO, I repeat, NO NO NO reliable signs of over pressure that you can read from a case, except case failure, and that is not the sort of sign you should ever see. a 9mm runs at about 1/3 of the pressure of a super magnum, and it is using about 5-10% of that total powder charge. The very idea that you could use the same primer characteristics to guess at accurate pressure gauging is ludicrous.

The only thing I have ever read that made any sense was to take a micrometer, and measure case heads at exact places indexed to the head stamp. When the case head expands by 1/100" or more, you are on the ragged edge of blowing your case open.

WESHOOT2 · May 13, 2010, 12:50 AM

"When in doubt throw it out"

Actually, throw it into a 'scrap' can, as your skills and knowledge grow you can revisit the can to see how smart you were at the beginning......
Plus scrap brass has value.

I follow my rule avidly.

FEG · May 13, 2010, 01:28 AM

All of the above is good advice, but it sounds like you don't have a reloading manual. My honest advice is to order a manual (or two) tomorrow. A lot of the information you will find on the internet won't even make sense until you read a competent manual.

The Norma manual is by far the best at explaining the manufacturing and reloading processes, but it has limited value as a source of reloading data (Norma components only). This is also true of the Dynamit-NobelSport manual, but I doubt you could even find a copy today.

Of the more "mainstream" manuals, I think Speer is the best at explaining these issues. The data uses Speer bullets and bullets cast from RCBS molds.

The Lee manual doesn't use enough pictures in my mind, and the data is just a compilation from free sources. A lot of ink is wasted on hyping Lee products. (I am going by the 1st and 2nd editions; I don't even know if they have any later editions.)

Lyman is the best data source, since they develop loads using a variety of different manufacturers' bullets. I don't think the explanatory sections are as good as Speer.

Hornady does a decent job of explaining the processes, and most reloaders will eventually use Hornady bullets, at least to some extent.

Most of the other manuals are specific to that brand's bullets, such as Sierra, Lapua, and Barnes. There's nothing "wrong" with them, but a new reloader probably isn't going to spend that much money on bullets for his/her first efforts.

Eventually, you may wind up with ALL of them. I have all of the manuals listed above in at least one edition, except Barnes.

SL1 · May 13, 2010, 07:57 AM

But, the answers tended towards talking about pressure signs for an unsafe powder charge.

Cases that might be unsafe are ones that:

have obvious cracks
have obvious corrosion pits
have obvious large bulges (some debate this)
have sharp creases or deep, sharp-bottomed dings
have loose primer pockets
have "incipient head separation"

This last one is mainly a rifle case issue, but can apply to the newer, really high pressure handgun cartridges, too. And, it is the least obvious. It is a thinning of the case wall in a ring around the INSIDE, down near the web area. SOMETIMES it makes a brightened ring around the outside of the case in the same location, and sometimes it doesn't. And, sometimes scraping the case pressure ring through the sizing die will make a bright ring on the outside that looks similar to an incipient head separation. SO, the only way to really find an incipient head separation is to check the INSIDE of the case. The usual way to to that is to use a piece of wire with a little section bent at a 90° angle. Stick that down into the case until the end touches the bottom, then drag the bent-out end up the case wall, "feeling" for a groove in the wall that runs around the case wall on the inside. This takes some practice, so when you THINK you feel a groove, section the case and SEE what you are feeling. Soon, you will calibrate yourself to know what a real thinning ring feels like.

One other issue that is not really a safety issue, but is important. Clean your cases and check them for grit BEFORE you run them through your dies. This is especially important for auto-loading guns that have thrown the cases on the ground, where they can get bits of grit imbedded in the brass. Those bits of grit will PROMPLTY scratch your dies, which will then scratch ALL of you cases.

SL1

May 12, 2010, 08:42 PM	#1
jambrdly Senior Member Join Date: January 31, 2010 Posts: 105	how to tell if a case is safe? Hello: I'm fairly to new to reloading and I was just wondering if someone could tell me what the visual or measurable signs of an unsafe case are? Also, if there is a website that perhaps shows examples? I have read about "cratered primers" for example but I have no idea what visually distinguishes a cratered primer from a normal fired primer.

May 12, 2010, 10:05 PM	#3
dmazur Senior Member Join Date: July 5, 2007 Location: Pacific NW Posts: 1,310	Brass can stretch, and some reloaders look at changes in case length as an indication of overpressure. Since this is affected by work-hardening and brass alloy, it isn't reliable. Similarly, the primer can "flatten" and fill the gap between the primer and primer cup. It can even make the cup larger in diameter. This doesn't always occur with overpressure. The primer can "crater", or show brass flow up around the depression created by the firing pin. This can also be caused by excessive clearance between the firing pin and firing pin hole in the bolt, so it doesn't necessarily indicate overpressure. The head can show ejector marks. This can also be caused by the presence of lube in the chamber, so, again, this isn't a reliable indicator. With the variation in barrel performance, even a chronograph reading that shows you are "in range" for a given load won't prove whether you are experiencing overpressure or not. Almost everyone would agree that if you see all the signs listed above, you are probably overpressure. However, no single visible (or velocity) cue is proof. An instrumented barrel, using RSI transducers and software, is probably the best indicator. Around $600, I believe - http://www.shootingsoftware.com/pressure.htm Anything else is guessing. Perhaps educated guessing, but still guessing. __________________ .30-06 Springfield: 100 yrs + and still going strong

May 13, 2010, 12:50 AM	#5
WESHOOT2 Senior Member Join Date: February 20, 1999 Location: home on the range; Vermont (Caspian country) Posts: 14,324	easiest solution "When in doubt throw it out" Actually, throw it into a 'scrap' can, as your skills and knowledge grow you can revisit the can to see how smart you were at the beginning...... Plus scrap brass has value. I follow my rule avidly. __________________ . "all my ammo is mostly retired factory ammo"

May 13, 2010, 01:28 AM	#6
FEG Senior Member Join Date: July 14, 2008 Location: Indiana Posts: 324	All of the above is good advice, but it sounds like you don't have a reloading manual. My honest advice is to order a manual (or two) tomorrow. A lot of the information you will find on the internet won't even make sense until you read a competent manual. The Norma manual is by far the best at explaining the manufacturing and reloading processes, but it has limited value as a source of reloading data (Norma components only). This is also true of the Dynamit-NobelSport manual, but I doubt you could even find a copy today. Of the more "mainstream" manuals, I think Speer is the best at explaining these issues. The data uses Speer bullets and bullets cast from RCBS molds. The Lee manual doesn't use enough pictures in my mind, and the data is just a compilation from free sources. A lot of ink is wasted on hyping Lee products. (I am going by the 1st and 2nd editions; I don't even know if they have any later editions.) Lyman is the best data source, since they develop loads using a variety of different manufacturers' bullets. I don't think the explanatory sections are as good as Speer. Hornady does a decent job of explaining the processes, and most reloaders will eventually use Hornady bullets, at least to some extent. Most of the other manuals are specific to that brand's bullets, such as Sierra, Lapua, and Barnes. There's nothing "wrong" with them, but a new reloader probably isn't going to spend that much money on bullets for his/her first efforts. Eventually, you may wind up with ALL of them. I have all of the manuals listed above in at least one edition, except Barnes. __________________ WARNING: CZs MAY BE HABIT-FORMING. Consult your doctor if nursing or pregnant.

May 13, 2010, 07:57 AM	#7
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	The OP asked about signs for an unsafe CASE. But, the answers tended towards talking about pressure signs for an unsafe powder charge. Cases that might be unsafe are ones that: have obvious cracks have obvious corrosion pits have obvious large bulges (some debate this) have sharp creases or deep, sharp-bottomed dings have loose primer pockets have "incipient head separation" This last one is mainly a rifle case issue, but can apply to the newer, really high pressure handgun cartridges, too. And, it is the least obvious. It is a thinning of the case wall in a ring around the INSIDE, down near the web area. SOMETIMES it makes a brightened ring around the outside of the case in the same location, and sometimes it doesn't. And, sometimes scraping the case pressure ring through the sizing die will make a bright ring on the outside that looks similar to an incipient head separation. SO, the only way to really find an incipient head separation is to check the INSIDE of the case. The usual way to to that is to use a piece of wire with a little section bent at a 90° angle. Stick that down into the case until the end touches the bottom, then drag the bent-out end up the case wall, "feeling" for a groove in the wall that runs around the case wall on the inside. This takes some practice, so when you THINK you feel a groove, section the case and SEE what you are feeling. Soon, you will calibrate yourself to know what a real thinning ring feels like. One other issue that is not really a safety issue, but is important. Clean your cases and check them for grit BEFORE you run them through your dies. This is especially important for auto-loading guns that have thrown the cases on the ground, where they can get bits of grit imbedded in the brass. Those bits of grit will PROMPLTY scratch your dies, which will then scratch ALL of you cases. SL1

May 12, 2010, 08:44 PM	#2
mrawesome22 Senior Member Join Date: November 9, 2005 Location: Ohio, Appalachia's foothills. Posts: 3,779	You need a reloading manual. Try a search for "over pressure" or "excessive pressure".

May 12, 2010, 10:16 PM	#4
briandg Senior Member Join Date: May 4, 2010 Posts: 5,468	there are NO, I repeat, NO NO NO reliable signs of over pressure that you can read from a case, except case failure, and that is not the sort of sign you should ever see. a 9mm runs at about 1/3 of the pressure of a super magnum, and it is using about 5-10% of that total powder charge. The very idea that you could use the same primer characteristics to guess at accurate pressure gauging is ludicrous. The only thing I have ever read that made any sense was to take a micrometer, and measure case heads at exact places indexed to the head stamp. When the case head expands by 1/100" or more, you are on the ragged edge of blowing your case open.