SmallCaliberCentral

I was preping some of my once fired brass today and noticed something strange on the case. About 0.281 up from the case head you can see a slight ring mark in the brass, when you run your finger over it you can feel its definately a bulge, below the bulge measures about 0.370 (strange as I thought the case head should be .378) just above the bulge it measures .378, the strangest thing is the bulge isnt all the way around the case and only goes around about 1/2 the circumference of the case. I can only think that this is caused by the case being loose in the chamber and resting on the bottom of the chamber leaving a gap at the top so once its fired it bulges at this slightly odd shape to fill out the top of the chamber. What do you guys think? Do you think this would have effected accuracy due to the shape the bullet would have been lying in the chamber? I am not that bothered by it just curious about the cause. The case doesnt look that pretty but I suppose that its now fireformed to my chamber.

The case shouldn't be laying in the chamber. It should be gripped by the bolt. Can you get a picture posted of it? Could be case head seperation.

Hi glen thanks for the reply, I have tried some pics but its hard to get them clear, I dont really know what you can make of these. I know what you mean about the cartridge shouldnt be lying, Its strange the bulge is only part of the way around and that where the bulge starts is actually the proper dimension for the case head at .378 whereas the case head at .370 would seem undersized, I have about 200 brass and they all seem to be like this

craigyboy

What rifle were these fired in? Are these out of your Cooper?

Mine are all like that. From once fired thru 6x fired. I have a 700ADL. They also measure .374" on the rim & .376" at that ring.

I really think that they are tilting in the chamber as the firing pin strike is off centre towards the top of the primer where the bulge is, so this would give even more indication that the cartdridge is lying down at the bottom of the chamber as the pin is hitting the primer higher up and then the brass bulges too fill the gap at the top of chamber, not really too happy about this now that I think more about it.

That's pretty typical for today's undersized brass (which I've fussed about a LOT around here!). I wouldn't worry about it, just don't size it down to "normal" looking, leave it big, so it doesn't overwork the cases, and consider it "formed" to your chamber. Or, you could send the rifle back to Cooper, but that's a hassle from overseas. IF the companies would make their cases to spec, that wouldn't happen (hopefully!) but they are ALL skimping on brass these days, almost all of it is undersized to some degree.

thanks Glenn, this is very annoying and I know its gonna bug the heck out of me, as now this means that the cartdrige is canting in the chamber so the bullet isnt produced to the barrel exactly square and also because the bulge is on one side of the case making it off centre and depending on which way I drop the bullet into the receiver will depend on which way the bullet is sitting canted in the chamber i.e in my mind producing a big variable I am going to have to drop them in with the bulge facing the same way all the time, what could cooper do if I did send it back to them? Maybe this is an excuse to have a lother walther match grade barrel stuck on in a couple of years (always have to have a good excuse for the little lady)

About all Cooper can do is set the barrel back and rechamber, perhaps with a newly sharpened reamer, which would make the chamber smaller. Personally, I wouldn't worry about it at all, it's a brass thing, not a rifle thing. If it makes you feel better to orient the round to the chamber the same way each time, do so, but it might be best to run a test to see if that makes any difference at all. Given the vagaries of shooting ability on any given day, it might not make any difference that you can quantify.
I know for sure that I have days when I'm just not shooting well, so I don't get too worked up over things if one day goes badly.
I guess the real question is, is the rifle shooting well enough to satisfy YOU If so, don't worry, be happy, if not.........

That is the first sign of case head seperation.

Use a paper clip, with the end bent at a 90 degree angle (1/8" long), and sharpen the end to a point.

Reach in the case and see if you can find the ring, if so, discard the brass.

Possibly sizing too much, oversize chamber, or??? The face of the bolt should hold the case in the chamber. Yes, the bolt head does as well, but if the cases are sized to minimum, or near minimum, your fired brass should fit your chamber like a ....well...you get the drift.

My savage does the same thing with win brass no worrys here as I have cut cases length wise with a dremel tool that have ben fired six times with no signs of case head seperation ( Meaning no crack or thinned brass in that area of the web) just a brass thing as stated above. I get the same 1/2 the case buldged thing too and after six loadings its all the way around now rather than 1/2, but once there formed I dont worry about how they are feed in to the camber because accuracy remains the same or better. I also bought a no-go gage to make sure and the no go wont chamber thats always a good thing.

Matt

Take a look at the brass in the picture in the article Silverfox wrote. The bulge in the brass pictured is normal. This is just the brass conforming to the chamber where the bolt and chamber meet.

http://www.rugerhunting.com/fire_forming.php

This article has some pictures of actual incipient case head separation.

http://www.the-long-family.com/fireform ... -250AI.htm

Brass I shoot in my XR-100 shows the same bulge as the brass in the pictures of Silverfox's article. One of my first posts here was about this very subject. I still have and shoot the same brass that I was inquiring about back then. My custom Panda doesn't cause the same bulge in the brass as my XR-100. The difference is that the brass is so much tighter in the bolt face of the Panda than the XR-100. Take one of those cases and place it in your bolt face and see if the bulge starts just at the top of the bolt face. The worry I would have is determining whether the bulge is due to incipient case head separation or not. The paper clip trick mentioned earlier can help you feel if this is case head separation or not. I can't tell by your pictures.

Here is a picture of what an actual case head separation looks like. NOT a pretty picture. When in doubt, toss it out.

http://www.thegunzone.com/sig239-kb.html

What you are seeing is purely an example of undersized brass that is fairly common these days.

Incipient case head separation shows as a bright ring running completely around the brass with no bulging of the case occurring. If you've never actually seen it before, bump the shoulder back on one case and fire it seveal times that way. You'll quicky see what the ring looks like.

And a sharp paper clip will allow you to easily feel it inside the case as was mentioned.

-BCB

I have a Cooper Phoenix in 204 Ruger that is doing the same thing as yours. I'm taking it to my smith Monday to have hime look at it and make recommendations. I measured new unfired WW brass at the place of the bulge and then the same brass once fired. Unfired it measured .370" and once fired .3775". So it expanded .0075" which seems to me to be excessive, and it's bugging the #$%^& out of me!

After speaking with my smith he said that we might set the barrel back and just rechamber again with his reamer which as tighter specs in that area that is expanding.

Anyway....I will update later with results after taking the rifle to him.

Phasor

I also have the same issue with my Savage VLP. Everything shoots fine so I wasn't too worried about it. I have only fired new brass so I guess I'll see what happens after sizing it. I'm still building up my stock of OF brass for Prairie Dogs.