It just came to my attention that my Redding neck size only die is leaving a truely strange resizing ring on the neck of my 7mm STW. That is there is as a result of neck sizing only of both new and once fired brass. For lack of a better description I saw what looks like a "sharkfin" in an otherwise perfectly round sizing mark from where the die worked the brass. If you were to look at the case neck one can see the perfectly level line formed from neck sizing, then the shark fin appiers then the sizing ring goes back to being level again.

The shark fin is brass that has not been worked. What is most baffling to me is this does not happen on every piece of brass, and happens on both new and once fired brass, as well as brass from compleatly different lot numbers. I have taken the die apart and inspected it and cleaned and could find nothing wrong.

As this is occuring in new never fired brass, I doubt that it could be the rifle causing this, or the bullet seating die, or anthing else save for the die itself. But the fact it does not happen every time I reck size it could be somthing besides the die.

I have a RCBS Rockchucker press, and use Redding shell holders for all reloading proceadures. I dont think the press is at fault as I reload other calibers with it, and no similar problems (or any problems for that matter) have emmerged with thoses Redding dies.

I have since sent the die set back to Redding along with a example of a problem case. I hope thay can find out something as I am at a total loss as to why this is happening.

Any thought would be appreciated.

Thanks Art.

A picture of what you're describing would be worth the proverbial 1000 words. The fact that it's not consistnat and on new and fired cases causes me to conclude you may be using too much lube. Clean your dies, making sure that the air vent is not plugged, then lightly lube the case neck outside (preferably with Imperial Die Wax, from Sinclare). I mean LIGHTLY...like dabbing the pad of your finger in the wax then rolling the case between your finger and thumb.

It sounds to me like you are doing something to cause the case to enter the die at something other than square. Like maybe it's not centered on the shell holder or the shell holder is not centered on the ram. Have you thrown away the silly little clip that holds the shell holder to the ram yet? Jim

I do hope you find the trouble with the "shark finning" of the cases. Might be a lube problem. I have seen some crazy things come from lube and lube pressure. And according to many it can't be the die, after all it is a Redding! Yeah and I have a bunch of beach front property in North Arkansas! Good luck!

Is there a vent hole in the die in the neck area? I've had similar witness marks from dies that have vent holes with even minor burring or just sharp edges around the hole.

A picture would sure help. roger

Thanks to all who took the time out to help me with their thoughts on this matter. For the sake of brevity, I will say that I allowed for or checked all of the potential causes for my problem suggested and found none of them.

The good news is I received my dies back today from Redding with a new neck sizing die and with a short explanation sateting that the "die has a machining defect at beginning of neck inlet".

The main reason I felt this problem was most likely not caused by anything I was doing is it was unique only to this caliber and this neck sizing die. When I used my Redding dies to reload my .338wm, .300wm, and 6.5x55 I had no trouble what so ever, and I use the same exact reloading procedures for them as I do for my 7mm stw. Also as I examined the sharkfin abnormality under a magnifying glass it quite evident by the sharpness by which the sharkfin was impressed into the brass it had to be caused by the die itself. The line formed by the sharkfin was just to sharp and well defined to be caused by excess lube, especially since i use Hornady "One shot" quite spairingly, and have made a lubing block so that only the necks of the brass are exposed and get lubed when sprayed.

To answer the picture question, take any platic pop bottle that has eithor a extrucion ring in the top edge of the plastic or at the top edge of the lable and any where along eithor edge sitting exactly on top of as you look at it, just immagine a sharkfin shape with the flat or back side of the fin to the right and the curved part to front, and thats what it looks like. Or even simpler, just draw a strate line and anywhere in it draw a right side up sharkfin as if it were swimming right to left, then wrap it around the case neck and thats what it looks like.

I will say I am extreamly pleased with Reddings customer service and turn around time. When I spoke to the CS rep from Redding he was helpfull and polite.

Again thanks to all for your input and for the time it took to do so.