SmallCaliberCentral

These 204's were new cases that I loaded up and this is what I ran into. There is a slight ridge about 1/4" up from the case head. The brass looks different towards the case head as well. It's like it's shinier than the rest of the brass. These were loaded 0.5 grains under max and shot out of an AR. Primers looked good and velocities were well below published max for this load. WW brass. Any ideas?

Pull back another 6" and take the picture again.

Believe your chamber is just a touch large. Probably within spec, but on the large side.

Does a new piece of brass wiggle side to side in the chamber???

If you cut that brass from top to bottom, you would see that lowest part that didn't expand is almost solid brass-it is called the web. The larger part of the case which expanded did just what it was supposed to do, fill the chamber. I can see the same thing on my fired brass, but not quite as distinct. You probably have a slightly larger chamber than mine.When you re-size with your die the case will go back to straight. Brass fired in your chamber will work a little harder than if fired in mine because of the stretching, and so it might not last for as many loadings.

Most brass failures are split necks, worn out primer pockets, or split at the web.

acloco and Hotshot got it, your chamber is large (very large).

No, this is not a sign of high pressure, your o.k! Shoot away...

As Hotshot said, I see the same line on my brass at the web junction, just not as pronounced.

You might want to strech a bit before you try and resize though, and maybe a protein drink after...

Just thought I'd add:

Make sure you set your FL sizing die to bump the shoulders back around .002.

What do you semi shooters think? I do not own or load for one myself.

On a bolt gun I would consider .002 a little excessive.
In a semi its probably considered tight.

You want to size them just enough to properly function. No jamming and more importantly the bolt needs to close and lock up fully.
Size them too much and a chamber like that will be chewing up brass almost as fast as bullets.

"Incipient Case Head Seperation" is something all reloaders should read and become familar with.
It happens, I've seen it

I checked some once fired HSM and Hornaday Factory loaded brass as well. They all show this same issue to some degree. I took some shoulder measurements on several cases.

---------------HSM----------Hornaday----------WW(new brass I loaded)

Pre-fired---1.553---------1.553--------------1.549 - 1.551

Once Fired-1.554---------1.556--------------1.554

All good and accurate advice.

I'll add that this is one of the reasons some of us go with custom reamers when screwing on a new barrel. The new Pac-Nor 11 twist 204 Ruger Match barrel I just put together on my M700 action employed a custom reamer with all the SAMMI dimensions tightened up all around, neck, body, etc.

A fired case out of that chamber does not exhibit any of the chamber bulges shown above, so cases should last a very long time in that rifle. However, a case fired in my factory Sako 204, even after F/L sizing, will NOT even chamber in the M700. So all brass for both rifles must be segregated. (The accuracy advantage of the custom chamber makes all this well worth the effort.)

As mentioned, shoot away, but you'll want to be F/L sizing every case for that rifle, as the chamber is definitely on the large side of SAMMI spec.

Do you have a micrometer that measures in the 10 thousandths? Would like to see the cases measured to the 4 decimal.

Honestly, I would ask for a new barrel. Any time that a cartridge looks like this, the reamer floater has not been serviced properly, set up properly, machinist turning the barrel too fast, or the machinist is not paying attention to what they are doing.

I have a buck that says they are spinning the barrel too fast and the reamer floater is not floating well.