resizing question

[Chimpy]

After sizing a case I am getting around .006 runout on the case neck. It dosent seem to make a difference neck sizing or full length. Before sizing I am getting .002 to.003. I am using the same rcbs press and dies since 1977. Not sure where to start looking for the problem.Any suggestions ???

 

[groupshooter22]

Are you using an expander on your die? They will cause run out.

 

[Toby Bradshaw]

If you're using an expander ball in the dies, take it out and check the case neck runout after sizing without the expander ball. If the runout is lower, the expander ball is the problem. If so, bushing dies, or custom dies, are the solution.

Toby Bradshaw
baywingdb@comcast.net

 

[fdshuster]

Chimpy: Ditto to what Toby said, an off-center expander can and will pull the case neck out of alignment, and one of the main reasons most of us do not use them. Look at the underside of the sizer die and see if the de-capping pin appears centered in the opening? The pin may have been centered when new, but if you're decapping a primer and the case has an off-center flash hole, the rod will be bent-- forever. I've seen new, unused sizing dies, right out of the factory box that have off-center decapping/expanding rods. If you must use the expander, I've found the floating carbide button types to be the least damaging to neck alignment, and of course, a little lube on the inside of the case mouth may help. As Toby said check results with and without the expander.

 

[cmillard]

is this brass fireformed?

 

[jo191145]

Chimpy
Like Toby said, test with and without the expander. If it is the expander causing runout heres a tip. Put a rubber O-Ring between the die body and the expander lock nut. This will allow the expander/decapping rod to free float. I'm not much of a fan of expander balls myself but when I use them I always have some rubber in there.

Another thing to look at. With no die in the press and the ram fully raised, measure from die mount to ram on four sides. Need to use the depth quage on your calipers. The top of the ram can be out of square with the top of the press. Mine was, quite a bit actually. I filed the top of the ram until it measured the same all around.
I've also heard the shellholder retaining ring can cause runout. I removed mine years ago.
Takes a little getting used to operating without it but I do not miss it anymore.

 

[Winchester69]

How do two individual dies, each with their own expander button, give the same run-out? Probably not the brass, since it was better off before sizing. What's the history of these dies? Have they ever given better run-out measurements? Do any dies give good run-out measurements?

 

[infantrytrophy]

Here is a link to an article in German Salazar's blog. Probably the definite word on seating die runout.

http://riflemansjournal.blogspot.com/2009/09/reloading-seating-die-runout.html

Randy Sikes

 

[jlmurphy]

Have you checked a fired case for runout? If the chamber is poorly cut, the sizing die may not be able to remove the runout.

 

[Chimpy]

Thanks for all replys and info. I have just recently started checking for runout, I removed the expander ball and it was the culprit. I learn something new everyday.

 

[Dimwit Flathead]

One other thing you can try is to run the expander ball to the top of the die so that it just allows the case neck to enter that section of the die. You will get straighter case necks doing this, but you'll also have to decap in a separate operation. Those of us who use Forster FL dies already know this trick.