Learing the importance of case inspection - again

[119er]

Learning the importance of case inspection - again

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A little while back I had a case separation in my AR-15 from using once fired military brass. I made an assumption that it being once fired was no cause for concern as I thought that these would be like other military cases I have used. The main difference being that a lot of my previous military cases were unfired from pull downs or over runs. I assumed that separations shouldn't occur until several firings.

Wrong.

Today I was sorting the brass from the range trip that the broken shell occurred on and took Walkalong's advice and ran a dental pick down the inner body of each case. Actually, the first case I picked out of the tub had a bright ring around it. That is what triggered my memory to use the pick. Well out of several hundred cases two were discarded and I cut one of those open to show what I found. It almost certainly would have separated the next firing. This will now be a permanent part of my sorting routine. All others already sorted will be done when resizing.

The photo doesn't show depth very well but the ring is pretty deep. It is easily felt with the pick.

Moral of my story: Try not to make assumptions like I did or become complacent. I knew better, but wasn't thinking about the prior history of those cases. I think this can be easy to do with time constraints, components being used months or years after purchase, etc.

 

[gamestalker]

IMO, that case appears to be a bad piece of brass. Most incipient case head separations occur down lower, about where the resizing die stops. I've had dozens of incipient separations over the years, few have ever leaked, but they have all been right above the case head, this the term case head separation.

I'm sure someone else will be along shortly to help diagnose the possible cause of what you are experiencing.

GS

 

[Walkalong]

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Yep, that one is toast. Why wonder if all of those range cases we picked up are OK, when it is so easy to check them.

The rut is often lower, but not always, and it can be higher.

Good catch.

 

[grogetr]

When checking for this ridge in the case will it be all the way around or can it be only part way. Can the pick be used in one spot on the case or do you need to work all the way around. Thanks

 

[Walkalong]

I work it around in two or three places. Only takes a split second more.

 

[rg1]

I worry about case separations too. I've used the bent wire feeler method and also after sizing and depriming I shine a penlight into the primer flash hole and look inside the case with a head magnifier lens. The shallow depressions are clearly visible. I've put off buying the RCBS Case Master gaging tool which has the probe and dial indicator for checking inside cases. I think it'd be a great and fast way to check for the stretch ring marks. Luckily I've never had a separation in any caliber, knock on wood. I've bought a lot of once fired military brass. I normally see anywhere from 10 to as many as 50 or more out of a 1000 round lot showing some stretch rings. I wonder about the case in your picture. It is in the thick area of the brass and with proper headspace after sizing I wonder about the chance of separation? Some stretch rings are much deeper and the walls much thinner, but I too scrap brass like in your pic. I have suspected that the full auto weapons that military brass is fired in actually fires without complete bolt lock-up causing stretching or if it's just bad brass or one rifle with excessive headspace. Anyway it's very important to inspect for stretching to prevent separations and to have a gauge to measure case headspace you size for your rifles. These rings can show up close to the case head, a little farther up like your example, or even worse up closer to the thinner neck area usually in my experience close to where the annealing color stops on military brass.

 

[Savage99]

That 'dent' does not look as if it goes all the way around? I don't see it where the case was cut open!

What does it look like on the outside of the case?

I use a feeler wire on all fired cases.

 

[fguffey]

IMO, that case appears to be a bad piece of brass. Most incipient case head separations occur down lower, about where the resizing die stops.

It is assumed case head separation happens at a designated place/location. Google for images. Cases separating near the center of the case is common, not on large cases but on smaller cases. The shooter/reloader is going to have to consider, the case is locking onto the chamber in the front but not in the rear 'OR' the case is locking onto the chamber in the rear and not in the front.

Locking in the rear would be in conflict with the expert meaning the front of case traveled forward whole the rear of the case was held to the rear. Normally when the case is held to the rear the front of the case is blown out and fills the chamber, the case filling the chamber shortens the case (neck) causing confusion for the expert, Because: there is no differentiation between a case getting shorter from the shoulder to the case head and a case that gets shorter from the case mouth and case head.

Then let us imagine what would happen if the neck was too tight to allow the neck to pull back when the case filled the chamber. Anyhow I tumble my cases after sizing, I do not grease my bullets nor do I grease my cases.

F. Guffey

 

[Dr.Zubrato]

Yup!
Started checking my own cases, which if I'm honest was tedious as I load ~700 at a time..
But I caught one! Brass looked perfect, but the inside I felt a sharp rut, not a smooth one like you guys show. Brass had been reloaded close to 5 times, which is why I started checking my cases, since primer pockets and case necks have been holding up even with pretty stiff loads.

Props to Walkalong!

 

[rcmodel]

Cases separate where the thicker case web ends and the thinner case wall begins.

The location of the one in the OP is normally where they stretch and separate.

Stretching closer to the head in the thicker part of the web would be Very Unusual.

rc

 

[gamestalker]

I'm not arguing that's a case separation, it just doesn't look like the typical head separation. I don't think I've ever had one separate in the mid section like that before, and I do load em warm? Definitely a good example of why we need to inspect the entire body from head to shoulder though.

GS

 

[119er]

The root cause of the inspection was caused by a broken shell I posted here: http://www.thehighroad.org/showthread.php?t=760447&highlight=broken+shell

That 'dent' does not look as if it goes all the way around? I don't see it where the case was cut open!

I didn't bother to clean the edges up where I ground it on a bench grinder. It tends to smear the brass.

The groove is deep and there are a lot of scratches from me practicing catching a groove with the pick. I gotta keep it calibrated like my torque wrench elbow!

I was stubborn and honestly didn't want to spend the extra time adding another step to my reloading procedure. The broken shell showed me the error of my ways!

 

[rcmodel]

Then GOOD for You!

It is a necessary step no one should skip if they want to stay safe reloading bottle-neck rifle calibers!

rc

 

[fguffey]

The broken shell showed me the error of my ways!

119er. The case stretched, seems if a reloader could measure case stretch it would be possible to get out in front of case head separation. I am the fan of cutting down on all that case stretch by cutting down on all that case travel. I have rifles with different designs, one design forgives a reloader for bad habits, other designs are less forgiving.

I have fired 8mm57 ammo in an 8mm06 chamber. That does not mean much to most but the difference in length between the chamber and the case is .127".
Difference in length: From the shoulder of the chamber and the bolt face and the shoulder of the case to the case head. Everyone knows the case will not stretch .127" between the shoulder and case head, problem, reloaders assume the case stretches because they are conditioned to repeat everything they know every time head space is mentioned. One more time, not all receiver designs are alike and handle case stretch differently.

A friend built magnificent rifles. he built a few wildcats, in his first attempt to form cases he had 5 case head separations out of the first 10 attempts. I informed him I could have checked the rifle to determine if that would happen before he left the shop, I informed him I could have 'fixed'? the problem before he headed for the range and I informed him I could have met him at the range and 'fixed' the problem long enough to form the case.

F. Guffey

 

[Rule3]

I have had one 5.56 case separate. I do not recall exactly what happened at the exact time other than the rifle jammed with the body of the case in the chamber and a new round tried to chamber and got stuck in the split case body.

What is the worst that can happen when this occurs?

Was I just lucky and only had a to free the jam by removing the split case body?

Is there some way that some type of Kboom can occur??

 

[Walkalong]

The softer thinner front part of the case expands and seals the chamber to stop hot high pressure gases from escaping rearward. The harder case head is thicker, and does not expand in the same way (At least at normal pressures.), but it still has to hold together to stop those same gases, so it is thicker and harder. Remember, when we anneal cases we have protect the rear of the case from being softened. A soft (annealed) case head will blow.

So, if the case separates, the hot high pressure gases have a way out. How much depends. I don't believe in taking unnecessary chances, so I do not shoot brass until it separates. My opinion is that it isn't [strike]too bright[/strike] a good idea to do so, but some people do and think nothing of it.

It is not the same as catastrophic case failure, but it is a failure of the case to stop all the gases.

Do you feel lucky today?

 

[119er]

fguffey:

I am having trouble following your post. I will take that as you are suggesting I am oversizing my brass. Also, this post isn't directed at you in any way, just trying to clarify.

Nearly all of my brass is once fired military 5.56. To get reliable function on the first resize I have to size to the minimum on a case gauge. Just the way it works for me and I realize that this isn't the best solution, but it produces ammo that works. This is my first instance with failure in 5.56. I have tried to do the maximum dimension on the gauge but that causes jams(failure to chamber) as the body of the case doesn't seem to be sized enough on a number of cases.

7.62 is worse as the die will resize different cases different amounts and I check each one of those in the gauge. Some need two trips into the die to just to reach the case maximum(largest acceptable dimension). This has proven to function just fine in the M1A I fire those in. The AR's are less forgiving about what they chamber. After they are fired in my guns I can then bump the shoulder back just enough to be reliable.

I really like getting ahold of unfired surplus brass but it doesn't seem as common as it once was.

My solution is to check for stretched cases as I load to eliminate the problem

 

[Rule3]

The softer thinner front part of the case expands and seals the chamber to stop hot high pressure gases from escaping rearward. The harder case head is thicker, and does not expand in the same way (At least at normal pressures.), but it still has to hold together to stop those same gases, so it is thicker and harder. Remember, when we anneal cases we have protect the rear of the case from being softened. A soft (annealed) case head will blow.

So, if the case separates, the hot high pressure gases have a way out. How much depends. I don't believe in taking unnecessary chances, so I do not shoot brass until it separates. My opinion is that it isn't [strike]too bright[/strike] a good idea to do so, but some people do and think nothing of it.

It is not the same as catastrophic case failure, but it is a failure of the case to stop all the gases.

Do you feel lucky today?

No, I do not take chances either and would not deliberately use brass until it falls apart.
I am trying to understand the mechanics or physics of what actually happens with a case head separation.?? With the one case that I had, the next round fit nicely in the case body so I pulled it right out and kept shooting. It was a bad piece of brass.

In revolvers the cases may split and cylinder contains the pressure, In a semi handgun if a split happens it usually just fails to cycle and the slide jams,.

 

[Elkins45]

Cases separate where the thicker case web ends and the thinner case wall begins.

The location of the one in the OP is normally where they stretch and separate.

Stretching closer to the head in the thicker part of the web would be Very Unusual.

rc

Sometimes you just get an odd one:





This was a 270 that failed and blew the extractor out of a Savage 110. Fortunately it is a left handed rifle so most of the gas all blew out the vent hole and away from me. It was quite impressive when it blew a box of loaded ammo off the top of the bench next to me, and my right (support) hand caught a pretty good jet of hot gasses.

I have had case head separations before, but this experience was something altogether different because it happened to a part of the case where the chamber doesn't contain it.

 

[fguffey]

This was a 270 that failed and blew the extractor out of a Savage 110.

It had top happen, unsupported case head with excessive case head protrusion, no surprise it was a 110 Savage, the rifle that has an adjustable barrel that is said to be adjustable and followed by "Anyone can do it" followed by "All you gotta do is etc.."

I do not agree, it was not the 270 that failed, it was not the Savage that failed.

F. Guffey

 

[Elkins45]

It had top happen, unsupported case head with excessive case head protrusion, no surprise it was a 110 Savage, the rifle that has an adjustable barrel that is said to be adjustable and followed by "Anyone can do it" followed by "All you gotta do is etc.."

I do not agree, it was not the 270 that failed, it was not the Savage that failed.

F. Guffey

Well, this rifle in particular had fired several hundred rounds before this one, and it wasn't a home rebarreling job, so I place more of the blame on this particular cartridge case than I do the gun.

I do think it did a good job of diverting the gas away from my face. This experience is the one that really made me see the value of left handed rifles for left handed shooters. Every time I shoot a RH bolt gun off the bench I see that gas relief hole staring at me and remembering the force of that box of ammo being blown off the bench.