30-30...Reasons for split casings??

deegee said:
The shoulders look too rounded out to me.
Compare one of the empty casings to a new round if you have one left.

IMHO this is more than likely caused by one of the things I mentioned in my first post:
1) Someone decided to polish the chamber (possibly along with the action) and in doing so they rounded it out.
2) Correct me if I'm wrong, but afaik if there is excessive headspace (the gap for the rim with 30-30) the casing doesn't shoulder fully in the chamber and stretches, because the round is sitting further back at the bolt. I've not seen casings from an excessive headspace 30-30 rifle so I am not familiar with what they would look like.

You could compare these casings to another brand/box and see what you get.
I would just be careful of excessive fouling in the chamber from the cracked casings.
Click to expand...

But that's just it; in a cartridge that headspaces on the rim, the shoulder does not necessarily contact the chamber.
 
joe-nwt said:
But that's just it; in a cartridge that headspaces on the rim, the shoulder does not necessarily contact the chamber.
Click to expand...

I had a long technical reply to this regarding casing plasticity and back thrust etc., but there are too many unknown factors without seeing the gun and ammo. :)

As mentioned my first guess is a polished chamber. All of this may only be responsible for the rounded shoulders. It is still entirely possible that it was simply brittle brass on the cracked casings.

That said, if it were my gun I would seriously get the chamber checked anyway to make sure that it is not out of spec or modified.
Try a few rounds from a different brand/box to see what the results are.
And compare the shape of the fresh vs fired casings.
 
Is the gun chambered for .32 special? Just a shot in the dark.

You also have to realize that you're shooting Winchester ammo. Which I have had many problems with.
 
This is a brass problem, nothing more.
It is too brittle, and does not stretch enough to fill the chamber, so it splits.
The rounded shoulder is common on 30-30 chambers.
Regards, Eagleye.
 
Eagleye said:
This is a brass problem, nothing more.
It is too brittle, and does not stretch enough to fill the chamber, so it splits.
The rounded shoulder is common on 30-30 chambers.
Regards, Eagleye.
Click to expand...

I've shot .303's that had the brass shoulder expanding forward like a 1/4 inch(or close to it)...yes, the chambers were made that long on some of the wartime production guns. The brass was able to expand that much, totally fireforming it, without splitting.

Crappy brass...
 
As a few have already noted, the fired shoulder does not look right, it is rounded like a Weatherby magnum.

The case, as the pressure builds, forms in part to the chamber. A headspace gauge only measures the rim thicknes plus the spacing between the rim and the bolt face. Some stretching will occur, but in my case, the primers popped out. No, particularly in an older Marlin, the chambers were spot on.

Bad brass aside, if the chamber was of the correct dimension at the shoulder, the brass will NOT have an opportunity to deform (round out like that). I agree with some of the others that perhaps someone undertook some home made work and altered the dimensions of the chamber. I suggest bringing it to a gunsmith to have it safety checked for chamber tolerance.
 
Guys, the shoulder on a 30-30 cartridge is not as defined as some.

Those cases shoulders really don't look so far off.

It is a lever action, and the chamber is not gonna be a tight one.

The left is a 30-30 compared to a 30 Rem. just to show how the shoulders differ.

30Rem30-30Win.jpg
 
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