I have heard of this problem with other 7mmRUM's in various discussions on this caliber but until yesterday had not seen it. We loaded some 162gr a-max's with Retumbo in a buddies Sendero SF the weekend before and had NO problems. Last night on a hunt,..he fired one of the same loading,..and the case had collapse dents just below the shoulder/body junction about 180 degrees apart. Anyone know what this may be caused by?

I've had the same problem with my .358X.404. Where you using a fine ball powder? The indentations are elongated to the shoulder. The appearance would lead you to believe that somehow a pocket of gas was trapped and as the main contigent of gas was leaving the barrel this trapped gas pushed down and outleaving a depression about .100" wide X .030" deep X .250" long.I got some what I thought were poor answers from one of the gun nut rags but no one at the time seemed to have a good answer.I thought perhaps that particles of ball powder were being trapped and under high pressure between the two metals and the elivated temperature relative to that turbulant area of the case ignition and mometary entrapment accurred followed by the pressure release inside the case. Just a how could that happen possibility.It's been a head scratcher for me. roger

Two questions....

Do you have a picture of the case?
How much Retumbo?

JustC

I always assumed it was from the neck not sealing properly. I figured the brass had work hardened or else there was too much neck clearance. Could there have been any leftover cleaning fluid in the chamber?

knobmtn

Speer manual no 8= "Shoulder collapse is not common, but does occur, especially in magnum chambers with too much freebore when using slow burning powders. Some of the powder gas leaks past the neck of the case and forces the shoulder to collapse, usually blackening the entire case. Cases damaged like this should be discarded. A different powder may prevent a recurrence". I saw the same topic elsewhere, they said go to a faster powder or increase your powder charge if not at max loading.

I agree with the Speer manual. I had a case collapse just behind the shoulder when fireforming my blasted 375 Improved. I had seated all of the Speer 285 gr bullets backwards so as to reach the lands except for one bullet that was seated nose up. That's the one that collapsed.

The load was less than 70 grs of RL 15. That rifle has freebore.

The thing I have never understood about the Speer explanation is how , if the pressures on both sides of the brass are equal, does the brass collapse? Is the leaked gas sealed under higher chamber pressure and than pushes out after chamber pressure is exhausted? That at least seems to follow the laws of physics. roger

" Some of the powder gas leaks past the neck of the case and forces the shoulder to collapse, usually blackening the entire case." [image]C:\My Documents\2004-03[Mar]\dimpoled case.ipk[/image] Hopefully this is a picyure of an effected case just as it came out of the chamber a couple weeks ago. There was absolutely no blackening and this is typical of what I have experienced. Now if this picture doesn't come thru send me your e-mail addresses if you want a copy. This is the first photo I've tried to send and I really don't know if I'm doing it right. roger

"[image]C:\My Documents...."
This indicates that the pic is on your computer, not the internet. You can e-mail it this way (as a attached file), but to post it it needs to be on the internet (hosted on a server somewhere) so that we can link to it.

Thanks for the info roger

ricciardelli,...the load was 94gr of retumbo with a 162gr a-max in rem brass with a fed 215m primer. This load shot GREAT last weekend with no problems. It was set AT the lands. I seat .010" past my at the lands measurement and set deeper until the scars on the bullet jacket are very faint on non-existent. I have no problem saying that the freebore couldn;t have been any more than .005" with a big mistake made on the loaders part. The load shot great last week with NO MORE than a 10 degree change in temp. The bullets were form the same box,..the powder from the same conatainer,..and the brass is the same as well as the primer from the same box.



bartsche,..the powder was extruded grain (long) which never happebed with H870.



I'll se if I can post a picture. But,..Steve,..the marks appear like a vice grip were placed lengthwise on the case on tightened only partially. The collapse marks are lenghtwise on the case,..just below the shoulder/body junction and appear to be maybe .300" long.



The barrel was completely clean and the chamber was dried.

" The collapse marks are lenghtwise on the case,..just below the shoulder/body junction and appear to be maybe .300" long."

I've sent a picture to a couple of the guys on this thread that depicts exactly what you are describing. roger