Check the die for the vent hole, most likely it is hidden under the lock ring, so you'll have to unscrew that. These vent holes can get plugged with grease and dirt. Clean the vent and the die body there and the inside of the lock ring.

Redding dies do not have vent holes in them. Redding will tell you they don't drill them in their dies.

When I think back about dents in cases I have had more issues with Redding dies than other makes. I'm sure most people would agree that Redding may be the top end dies but they may not be perfect. Moving metal back when just touching the shoulder has caused small indentation just below the shoulder for me and I suspect that is exactly what Richard has identified. When the dents are above the shoulder I don't see how they can happen unless there is a venting issue either air or lube dents appear. Most lube dents I have seen are also elongated and run parallel with the length of the case where the dents below the shoulder run horizontal to the case body when the brass is compressed when setting the shoulder back. Charlie, at least you are not alone when it comes to mysterious dents in cases!!!!

OK, let me add some confusion to the discussion. I just took some close measurements of sized cases; Redding vs RCBS.

Measurement #1 was taken at the point of the case shoulder. The Redding sized case measured .459" and the RCBS sized case measured .4555"

Measurement #2 was taken just ahead of the extractor groove. The Redding sized case measured .468" and the RCBS sized case measured .4665"

So as least as it applies to the dies I have in my possession, the RCBS die actually has tighter dimensions than the Redding.

Applying my logic to this information would nullify the "moving metal" theory because the RCBS die, at least in this instance, sizes more than the Redding.

I'm leaning more towards a venting issue.

If you have an usized case you are willing to sacrifice take a small drill and make a hole at the neck shoulder junction to see if that will act as a vent and then try to size the case either with or without lube and see what happens.

260 Striker wrote:If you have an usized case you are willing to sacrifice take a small drill and make a hole at the neck shoulder junction to see if that will act as a vent and then try to size the case either with or without lube and see what happens.

7BR brass being as scarce as it is, I'll see if I can find a discard somewhere. I might have an old case with a small neck split for this purpose since I keep all those old cases to sell for scrap value. Thanks for the idea.