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Old March 31, 2006, 10:17 PM   #1
nimrodx
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Incipient Head Separation?

Hi Rifle Gurus,

I have a very accurate Sako rifle, that is less than 2 years old, and have
passed less than 300 rounds through it. 270 win

I have been using the same 100 cases throughout this time, and all
cases have probably been reloaded no more than 4 times.

I have been using fairly moderate loads.

Some of these loads may have been full length resized at least a couple of times,
but I have a neck sizing die that I know is easier on the cases. I tried to adjust the resizing die so that it was not setting the back the shoulder much if at all.

Some of the cases are now showing some odd characteristics. There is a 1/5 inch long
shiny partial circumference, 1/3 inch from the extraction groove on some cases. Using a
sharpened paper clip I seem to be able to feel a slight thinning in the case at the same point on the inside of the case.

Is this normal behaviour? It is very regular, and is being expressed in exactly the same way on each case.

Why? One batch of full length resizes were a little dirtier than they should have been and were a bit sticking in the resizing die...could this have placed too much tension on them when I raised the die?

Could this be a problem with the case manufacture?

Am I being a total ninny and worrying about nothing?

Any suggestions?

Thanks

Matt
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Old March 31, 2006, 11:24 PM   #2
Leftoverdj
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It's not normal. You are not being a ninny. I don't know much more that. You have a problem, but beginning case head separations don't show up on the outside of the case.

Find a gunsmith with the optical tool to examine the inside of your chamber under magnification. My guess is that the inside of your chamber was scored by a chip stuck on the reamer. The brass would be forced into the groove by the pressure of firing and then wiped off when the case is extracted. A bore scope should find that groove if it's there. I can think of nothing else that would give the symptoms you describe on a regular basis. The cases that do not show the mark would be those in which the pressure was slightly lower. I would expect it to show up every time on near max loads in slightly tarnished cases.

I dunno nothing about Sako's warranty policy, but, if I am correct, it's a factory defect and they should replace the barrel.
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Old April 1, 2006, 12:42 AM   #3
Rimrod
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nimrodx

What you described is exactly what the signs of case head separation are. The number one clue is the bright ring forming around the case just forward of the head, and you proved it with the paper clip.

It is difficult to say if the brass was defective since you have never used any others under the same conditions. If it was quality brass it probably isn't defective, some calibers are just harder on it than others. It would be a good idea to replace it though, if a round ruptures in the rifle it can send hot gas and debris in you face, gum up the action and the front part of the case may have to be dug out of the chamber if it completely seperates.

If your barrel had a defect it would show up on all the cases and they would have probably shown up with the first firing and would show where the case was inserted in a different way each time fired.
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Old April 1, 2006, 01:23 AM   #4
hoghunting
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I agree with Rimrod

That is case head separation and it will eventually happen to most brass depending upon the number of reloadings. I would buy new brass and keep on reloading, knowing you will have to buy brass again at a later time.
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Old April 1, 2006, 07:11 AM   #5
caz223
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If you smoked a fireformed case and set up your FL die to just bump the shoulder I don't know.....
You been keeping your chamber clean, cleaning only from the breech?
Maybe try loading to a longer OAL. Seat a bullet into an empty case way long, smoke it black, then try to chamber it. Note the marks on the bullet. Seat the bullet a little deeper, and repeat until it chambers. Set it back .010-.020 after it chambers and check your OAL. Is it longer than factory? Will it fit in your mag? Try loading this way, it may lower operating pressure
(and it might not.) and as a side benefit, maybe improve your accuracy.
Case head failures are nothing to laugh at. They're REALLY not funny in magazine fed autoloaders
Maybe you got a batch of bad brass?
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Old April 1, 2006, 10:15 AM   #6
dfaugh
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Yup, seen this one. You don't say what kinda brass you're using, but in any case, I've seen just what you described. After a few firings (4 or 5) we had some case heads seperate during resizing. These were also with mid-range loads, fired from a couple different guns.
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Old April 1, 2006, 11:44 AM   #7
Edward429451
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I get that here n there also. The rule is...when in doubt, pitch it out. Brass is cheap compared to guns or body parts.

If you got this on a few or more of those cases you might want to pitch the whole lot of it and buy new.
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Old April 1, 2006, 03:08 PM   #8
Leftoverdj
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I've seen partial head separations, but I have never seen them repeat exactly each time they occur. Some will be longer and some will be shorter. When you investigate with the probe, you find thinning around much or all of the circumference.

There is obviously something going and it needs to be identified and corrected before going further. That case separation can and does occur does not mean that's what's happening to this rifle. It could be the problem, but there is no real way to check over the internet.
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Old April 1, 2006, 11:46 PM   #9
nimrodx
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Thanks to all

Thanks guys for all that help.

I figure it is probably due to me getting my resizing wrong, but can't be completely certain.
LeftoverDJ, I am following your lead and taking it to a gunsmith.

I have player quite a bit with these cases (including seating depth), and that is
why I have done more full length resizing on them than I will in the future.

They are actually remington cases. I may purchase another brand next time, but only if the
gunsmith thinks it could be there fault, not mine or the rifle's.
Perhaps Lapua might be the go?

Thanks,

Matt
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Old April 2, 2006, 08:05 PM   #10
30Cal
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Here's one that's ready to give up just forward of the cannelure after 4 firings in an M1A (7.62mm LC89Match). I had the sizing die set such that the shoulders were being set back by 0.008" instead of the usual 0.004'ish. I had two full blown separations in this batch along with a bunch of others that had partials. The more subtle ones just had a little bit of a wrinkle.

If you're FL resizing without using a case gage to set the die, you stand a good chance of seeing these firsthand. Using the manufacturer's directions on how to set the die is just a half step better than guessing.

http://webpages.charter.net/tyoberg/...515_edited.jpg
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