.308 Brass - Impending Case Head Seperation? Pic inside...


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PowderMonkey
March 26, 2012, 11:11 PM
Hey folks. My last trip to the LGS I purchased a rubbermaid tub of 250 'used' .308 WIN brass for $24.

About 30% of the used brass looks like those shown below. I have already culled them aside. I tried the paper clip trick on them and could not feel a ridge or anything inside at that depth that 'caught' the paperclip - but like I said I've already culled the brass that looks like this - as my face and my high-dollar Armalite are too valuable to me to risk on a $0.10 piece of brass.

All the rifle brass I've ever loaded has been from new ammo that I fired, or factory bagged new rifle brass. None of my brass has had more than about 4 loadings on it, and I'm loading fairly light (70-80% of book max) so I have never seen anything like this in person.

Am I seeing what I think I am seeing? Impending case head seperation? Should I crush the shoulder and neck closed and put them in my recycle bucket? Did someone sell me 50% wore out used brass and 50% probably almost wore out brass... : (


http://www.jasonfagan.com/forumImages/308brass.jpg

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blarby
March 26, 2012, 11:26 PM
There is something seriously wrong with that.

May be case head sep, may be something else.

If you aren't familiar with the paperclip trick, it can be tricky to use... can you section one ?

IMO, without better pics, i'd say thats is indeed soon to be CHS, and wouldn't load them.

FROGO207
March 26, 2012, 11:27 PM
Cut a couple of them in half lengthwise and look for separation if you want to be sure. The marks look like where the links rubbed on the brass when it was pulled out of them. The brass was probably linked together for use in a machine gun and someone pulled the brass out of them and loaded it in a standard firearm to fire. Case head separation will be a wider band of brightly colored brass that has a frosty appearance. All of mine were at least 1/16 inch wide. Those are scratches on the outside.

blarby
March 26, 2012, 11:30 PM
Also possible.

I can see a little banding now........ better pics would help.

gamestalker
March 27, 2012, 12:30 AM
I noticed in the pics that #1 and #4 of those cases have what appears to be identical bands, at identical angles that bend down toward the web. It almost looks like the bands are showing a casting of a chamber defect, or somthing is in the chamber. But the brass looks quite different than what I'm used to seeing when my brass begins to separate. I shoot all my brass right ot the last loading so I am very familar with the initial signs, and the extended signs of separation.

If your taking good care to maintain the shoulders, you should be able to get 9 or 10 reloadings from your brass. I don't load for the .308, but I do load 06, .270 win, 7mm RM, and few others, and even though I run large charges of slow burning powders, I still manage to get 12-15 reloadings before they start the process of separation.

earplug
March 27, 2012, 12:36 AM
When I was a master gunner with a bunch of M60's that had head space problems. Many cases looked like your photo.
We were having lots of separated cases stuck in chambers.

evan price
March 27, 2012, 01:38 AM
To me, they look like the rifle they were fired in had a chamber that had a chatter mark in it.
I would take the worst looking one and hacksaw in half lengthwise and check the brass thicknesses. That would tell 100% for sure if there is anything to worry about.
If your paperclip test didn't feel a groove there may not be a groove. I've seen some M1 brass that had a line in it but it was fine.

P-32
March 27, 2012, 01:56 AM
I've seen this before on F/L sized brass. There is no problem as long as there is not a corresponding ring inside the case.

scythefwd
March 27, 2012, 06:50 AM
is the ring raised? It almost looks to be in the 3rd casing. If that's the case.. chamber inperfection. If not... if the peperclip don't feel the dip.. I'd use it.

bigedp51
March 27, 2012, 02:09 PM
Your marks are from the inside of your chamber as explained above and are raised bumps and imprints of your chamber, below are what case head separations look like on a .308 cartridge.

http://i122.photobucket.com/albums/o254/bigedp51/308failA.jpg

gamestalker
March 27, 2012, 02:22 PM
+1 Bigedp51 !! Those are some really good examples of the common place, and common appearance of case head separations. If that were my rifle, I would take it to a good smith and have the chamber examined and head space checked. That brass just isn't looking consistent with case head separation the result of normal wear and tear.

snuffy
March 28, 2012, 01:22 AM
Hey folks. My last trip to the LGS I purchased a rubbermaid tub of 250 'used' .308 WIN brass for $24.

If that were my rifle, I would take it to a good smith and have the chamber examined and head space checked. That brass just isn't looking consistent with case head separation the result of normal wear and tear.

Those don't look like incipient case head separation. But DO look like they were fired in a rough chamber.

PowderMonkey
March 28, 2012, 11:52 AM
None of this brass has been fired by me - I bought it used at a LGS.

Anyway I decided to fire up the scroll saw last night and do a little destructive testing. Pic with a real camera with macro mode now, as opposed to my initial camera phone pics. You can even see my pointy paper clip scrapes inside on pic #3. : )

Yes the ridge is raised but barely. One is not worse than the other - on the brass that have the mark, it's all the same.

http://www.jasonfagan.com/forumImages/308brass1.jpg

http://www.jasonfagan.com/forumImages/308brass2.jpg

http://www.jasonfagan.com/forumImages/308brass3.jpg

I can see no ridge or thinning of the case walls in the area around the ring. I'm assuming these are just fine and it was a rough chamber as many of you have suggested. I bet with a firing or two and subsequent full length resizing (all my 308 runs in both AR-10 & bolt guns) the marks may get ironed out and almost go away.

Thanks for all the replies!

PowderMonkey
March 28, 2012, 11:57 AM
I noticed in the pics that #1 and #4 of those cases have what appears to be identical bands, at identical angles that bend down toward the web. It almost looks like the bands are showing a casting of a chamber defect, or somthing is in the chamber <snip>

They all have that angled piece that veers off down towards the web. I just didn't have them all rotated to the same angle.

I'm totally settled now on - like you said - a casting of someone else's chamber defect.

Thanks!

Clark
March 28, 2012, 12:16 PM
Looks like the OP's smith did not brush all the chips off the reamer.

I chambered a 257RAI .004" too long. If I try to fire form in one step, I will always get separation at the shoulder from stretch.

Walkalong
March 29, 2012, 07:36 AM
Very good pics PowderMonkey. There is obviously no problem with that brass, other than the cosmetic issue, which won't hurt anything.

fguffey
March 29, 2012, 10:15 AM
Clark, I am sure everyone else believes a chamber that is longer from the bolt face to the shoulder .004Ē will result in a separation just behind the case body/shoulder juncture, I donít. Do not take it personal, it is a matter of keeping up with more than one thought at a time, measuring the case length before and again after (from the head of the case to its shoulder) and being able to measure the length of the chamber first.

Then there is that part where the model and design of the receiver information is omitted, and, it helps if the fire former has a very good understanding of what is happens when a case is formed when fired, 5 different chambers can be chambered with identical dimensions in different receivers and produce different results.

I did ask, do not to take this personal.

F. Guffey

Walkalong
March 29, 2012, 05:58 PM
I chambered a 257RAI .004" too long
I read that as .004 over accepted headspace, which would be more than .004 stretching. Perhaps I am wrong.

Clark
March 30, 2012, 04:34 AM
I chambered that 257RAI in 2002, nearly my first rifle I chambered.
I used a 257R piece of brass for a go gauge.
I did not know the the firing pin would crush Roberts brass into the Ackley chamber neck base, and then the case would get stretched.
All my brass get stretched in the same place.

What I learned to do [and I tried a lot of stuff] was 10 gr of any pistol powder, back fill with Cream of Wheat, no bullet and if forms half a shoulder that will stand up to the firing pin on the next shot. The next shot is full powder, full accuracy, and makes a full shoulder when done.

PowderMonkey
March 30, 2012, 06:21 AM
Thread drift! :neener:

fguffey
March 30, 2012, 09:42 AM
Powder Monkey, too bad you do not have the chamber that fired your cases, there is so much going on about stretch or flow, or both, with a chamber that imprints a shooter could keep up with skid marks as the case stretched and or flowed and if the case did stretch and or flow the shooter could keep up with the number of firings. As to the reamer? it is possible someone stuck a case in the chamber and used a creative way of removing it.

Clark, it does not seem unfair to most but my firing pins crush the primer before the bullet, case and powder knows their little buddy, the primer, has been crushed, meaning there is no way the case, powder, bullet can accelerate to a speed equal to or greater than the speed of the firing pin, and the primer does not have an avoidance mechanism, the primer is setting still when it is hit by the firing pin, so, there is a lag in time before all that weight of the loaded round (bullet, powder and case) catches up to the speed of the firing pin, well, that is the way it works in my rifles.

F. Guffey

cfullgraf
March 30, 2012, 09:47 AM
I tried the paper clip trick on them and could not feel a ridge or anything inside at that depth that 'caught' the paperclip...



Generally, with the paper clip test, I do not feel a ridge, crack, or other kind of discontinuity. I feel a thinning of the case wall. It is subtle.

It took a while and I probably tossed many good cases before I really knew what to feel.

That is not to say you would never feel a crack, but by that time the case is way past its useful life.

Clark
March 30, 2012, 07:16 PM
fguffey
..
Clark, it does not seem unfair to most but my firing pins crush the primer before the bullet, case and powder knows their little buddy, the primer, has been crushed, meaning there is no way the case, powder, bullet can accelerate to a speed equal to or greater than the speed of the firing pin, and the primer does not have an avoidance mechanism, the primer is setting still when it is hit by the firing pin, so, there is a lag in time before all that weight of the loaded round (bullet, powder and case) catches up to the speed of the firing pin, well, that is the way it works in my rifles.

F. Guffey


I wanted to explain my belief in firing pin push and started to think of equation for the firing pin spring force, mass, acceleration, cartridge mass, force... wait a minute, I am not going to derive the compliance of a primer cup shape... or how shared with cartridge acceleration. An empirical demonstration would be faster.

I took a 308 primed case, seated 220 gr round nose case deep, and wrapped about half enough tape I calculated to keep it centered in a VZ24 chamber that I converted to 300Win Mag. I took off the extractor. I pointed the rifle straight up and pulled out the bolt to making sure the cartridge was sitting on the bolt face.

I removed the extractor because, although it has no effect on the .004" of 257RAI case stretch, it would have a big effect on the visual of the primer dent.

All per what I expected the cartridge acceleration upwards with little denting of the primer.

What does it all mean?
The firing pin pushes hard and slowly on the cartridge, so the cartridge mass can easily accelerate away with little change to the primer, unless the cartridge is restrained. If the cartridge is restrained, the primer will go off.

eldon519
March 31, 2012, 04:43 PM
If you fire a primer in an empty case, the primer will also back itself out as far as possible and push the case forward. Same thing happens in a loaded round. The building chamber pressure stretches the case and re-seats the primer flush.

The 7th edition Hornady manual has a nice illustration of the process Clark has referenced and what I have added above. It is on pages 15 and 16.

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