Comments on: How to Improve Case Concentricity with Standard Seating Dies

By: Ralph

Ralph — Thu, 31 Mar 2022 11:14:57 +0000

I get the same TIR with standard dies and BR dies. I recently learned the press top bushing wasn’t even/level across nor was the die rings. I used 400 and 600 wet sand paper for both. I square off dies for TIR of .001 -.001 BRO seating with standard Redding and RCBS seating dies. Sizing…. .0005 neck TIR, along with .012-.0125 neck thickness. Full length neck TIR is usually
.0005 with turned necks. I have to use neck mandrels 21st century to achieve this.

By: Stihlman

Stihlman — Sat, 23 Jun 2018 15:54:29 +0000

No problem with my Forster coax press

By: steve

steve — Fri, 22 Jun 2018 17:38:54 +0000

This has been the most interesting and useful commentaries that I have read so far.
One question:
Why measure bullet runout near the case mouth?
I measure bullet runout halfway near the tip, I think that I get a better reading using the longer radius from the vgroove support.

By: MH

MH — Fri, 22 Jun 2018 16:34:19 +0000

I have tried endlessly to reduce case neck runout but what works best is to run a tight neck chamber.

Measure fired cases from any chamber and the neck is always concentric to the body… until you resize it.

The more you need to reduce the neck diameter the more opportunity to drift off center.

Conversely the less you need to reduce the neck diameter the less opportunity you have to drift off center.

Now short of custom chambers you can always just run thick neck brass like Lapua. That will help reduce the amount you have to reduce the fired neck to fit a bullet.

Since Winchester cases are one of the thinnest, they are also one of the most difficult to keep concentric… for reasons stated above.

By: BoydAllen

BoydAllen — Fri, 22 Jun 2018 16:20:59 +0000

If one has to use a one piece FL die that has not been modified, for loading cases that have not had their necks turned, doing the requisite neck expansion with a separate die and expanding mandrel will give better results. The neck IDs need to be lubed and the work done carefully. Also, when sizing you can lower the ram to some point where the expander is not engaged and turn the case half a turn and raise the ram again. This may improve concentricity. The same sort of thing can be done when seating, by seating half way, rotating and then finishing.

By: Boyd Allen

Boyd Allen — Fri, 29 Sep 2017 18:02:48 +0000

When working with relatively thin turned necks, and FB match bullets with pressure rings at their bases, I have found that when bullets are seated to engage the rifling that runout can reduce as the bolt is closed. To learn this I did a test where I intentionally caused a round to have .0035 runout and then chambered it and remeasured it. After being chambered with a neck clearance of about .0015 the round had .0015 runout. IMO the thin neck, relatively short bullet insertion into the neck and pressure ring combined to allow the bullet to pivot in the neck much like a ball and socket joint. Also, BT bullets tend to seat straighter than flat base. For chambers with larger clearances in the neck, and ammunition that is set up so that bullets do not engage the rifling, the entire burden is placed on the quality of the brass and the fit of the dies.

By: Gene

Gene — Fri, 29 Sep 2017 06:50:17 +0000

To ELR Researcher ;

Cold Heading tooling is all done “in the round”, as are reloading dies . The correlation I was trying to make was bullets , cases and chambers are all also “in the round” and the same geometry and principles apply to both .

Cold Heading tooling is used to make bolts and screws and other fasteners . And generally speaking ; at much tighter tolerances than the average reloading dies . Not quite sure where you came up with the idea that anyone making cold header tooling made loading dies , also . Though it wouldn’t be that difficult .

The response was in regard to a discussion of TIR and the comment Mike made regarding the impossibility of having a TIR greater than the size of the +.002 of chamber over-size . A bullet , a case , and a chamber . A circle within a circle , within a circle . Plus the thickness of the brass that will allow for a bullet to have a greater run-out than .002 …And still fit in the chamber neck area . The neck area of the case will fit in the chamber neck , but the bullet inside the case neck can be tilted by as much as half the thickness of the brass . Which can greatly exceed .002 run-out on the bullet .

By: ELR Researcher

ELR Researcher — Thu, 28 Sep 2017 23:35:00 +0000

Would be very interesting to see the results with the “Match” dies set up the way the standard dies were.

By: ELR Researcher

ELR Researcher — Thu, 28 Sep 2017 23:33:16 +0000

Gene – and who makes such reloading dies?

By: Gene

Gene — Thu, 28 Sep 2017 20:44:12 +0000

As someone who worked in the Cold Heading Tool & Die field for over thirty years ; and working in .0001 ( tenths ) I can state that you can achieve a greater bullet TIR than the .002 of the case O.D. TIR of .002 .

If the bullet is pressed into the case slightly crooked to start with, as all bullets are , it may , or may not straighten itself up as it is being pressed to full seating depth . You can check TIR of the case neck , and get .002 or less , and still have a bullet “running out” of eccentric TIR greater than the case . It will chamber in the +.002 chamber , but the bullet will still be out of TIR by at least half the clearance of the chamber , or .003 from Neck TIR .
In simple terms the bullet will be crooked inside the case , and the neck area in the chamber will not straighten the bullet as it is being chambered , because it is still within the Chamber neck clearance . But it will chamber .

This is exactly why Cold Heading Die pieces are made .0005 – .001 under-sized , and final lapped after assembly .