I don't see anything to get worried about. That looks like chamber or die marks. Here are a couple of mine. The one on the left is an R-P the one on the right is Starline. Notice they both have a mark almost in the same spot as you have. I am not sure how many loads these have had but at least 3 each.

 

I have frequently seen marks like this on 357 brass. Don't know what is it but seems to be common with straight walled cases.

 

JimmyBigLoop IMO looking at the Pic's that's where the resizing die stops :top: not the ugly bulge you don't want to see.

Maybe someone has a bulged case to post a picture of.

 

Isn't that circumferential line the spot at which the sizer quits working the case? I mean do sizer dies go all the way down to the rim? Now you got me thinkin. Could that line be the place where the case wall ends & the webbing or thick portion near the head begins? Even if the sizer does go all the way to the rim, the thicker part may resist the markings on the case wall. I don't know, just my 2 cents, jd45

 

As far as I know the sizer die comes all the way down but the actual sizing ring inside the die stops short on each caliber so this is probably where the sizer die's internal sizing rings are stopping. That's me two cents.

 

Yup it is where the sizing die stops on the right ones, maybe the left one too?

I'll put them through the sonic cleaner and see if they brighten up and loose the ring.

Thanks guys.

 

It's likely none of the above, and the shell goes into the die further than that.

What it is is the expansion ring. This is the juncture where the case wall does not expand to touch the chamber wall when it is fired, because the brass is thick enough to resist expansion. As the case proceeds toward the neck end, the brass becomes thinner and expands under firing pressures to "grab" the chamber wall. A measurable difference in diameter (before sizing) is present, and proof of what is happening.

When a case is about to separate, it is always above this ring, as this is the area above which brass stretches under firing forces.

Here's a picture of a case about to separate. Notice the crack, or faint bright line, is above the expansion ring.

The only cases that do not show an expansion ring have either never been fired or have fired such a light load that the case walls did not expand outward. The area below the expansion ring does not get sized by the die upon firing, as the factory sized diameter there is smaller than most die sets, and no burnishing of the brass under sizing "squeeze" occurs below the expansion ring (notice the darker brass below the expansion ring......not rubbed by the sizing die is why it's still dark). Which makes it more noticeable in sized brass, especially if the case tarnished a bit since the last loading.

Point is, it's not where the die stopped sizing. It's where the brass is thick enough that it didn't expand and therefore didn't get sized. I know that sounds like the same thing, but it's not. If the case had expanded further down, it would have been sized further down. It's simply where the case didn't expand at all.

It is perfectly normal.

 

Point is, it's not where the die stopped sizing. It's where the brass is thick enough that it didn't expand and therefore didn't get sized. I know that sounds like the same thing, but it's not. If the case had expanded further down, it would have been sized further down. It's simply where the case didn't expand at all. It is perfectly normal.

35remington very well put :biggrin: I knew someone would have good pic's too.

 

Interesting stuff guys, good to know.... Im not loading yet but its in my "knowledge bank" now....:hmmmm:

 

Way to really lay it out for us, 35remington! Thanx, jd45
BTW, I think it's about time you got promoted to a capitol "R" behind the "5". (grin)