Seating die induced runout

[Adam in WI]

Hi folks. To make a short story long, I've been rather unimpressed with the accuracy of my 6.5 prc. I won't name the maker until I get this all sorted out, but it's not a cheapo rifle. I've been struggling to get anything consistently under moa. After doing all the normal checks and even trying a different scope, I dug out my Sinclair concentricity gauge to check out my cartridges.

Lo and behold, I have some loaded rounds with .008-.010 tir runout. Fired cases are .001 or under on the necks, and my resized cases are .002 or under. For reference, I checked some Federal factory fusion loads that were .003 or under. That load shot reasonably well and easily beat most of my hand loads. Have I isolated the issue to the seating die, or is there something else I might be doing wrong? These are Hornady dies.

Also; Peterson brass out of the box has up to .004 runout at the neck. I'm guessing I should run them thru the sizer even though Peterson advises not to.

 

[RegionRat]

Have I isolated the issue to the seating die, or is there something else I might be doing wrong? These are Hornady dies.

Also; Peterson brass out of the box has up to .004 runout at the neck. I'm guessing I should run them thru the sizer even though Peterson advises not to.

There is ye olde saying.... one test is worth a thousand words.....

Ya, you will benefit from troubleshooting that issue some. You don't need perfection, but you are probably well over the threshold where runout causes issues. Good Luck and in for the range report.

 

[NF1E]

First suggestion would be even with new brass is to run a tapered mandrel neck expander to affirm concentricity ahead of time. Next dump the expander ball in your sizing die. Solutions abound, Whatta Hobby!

 

[L.Sherm]

I haven't measured runout on cases or loaded rounds in probably atleast 10 years, that being said I use only what I consider high end FL sizing dies and inline seating dies.
One exception is on my small sage rat stuff I still use other seating dies.

 

[AlNyhus]

Before doing much else, remove the shell holder clip from your press and substitute an 'o' ring. Seat a bullet and see if there's any change in runout.

 

[big5ifty]

...I've been rather unimpressed with the accuracy of my 6.5 prc.

What does 'accuracy' mean in your case ?

It's extremely unlikely that zero runout in the ammo is going to be the thing that makes the rifle shoot.

Any factory rifle is a hit or miss scenario. Most custom rifles are a hit or miss scenario as well, because almost no custom rifle maker will risk testing the rifle before giving it to you.

The only rifle you can trust is the one that comes with at least two verified 3 shot groups on paper, that show the required accuracy. That rifle will also come with it's ammo spec.

Having said that, excessive runout may cause accuracy problems, and if you're sure it's in the seating die, two things that cause runout in the seating die is a seating stem that

1. does not match the bullet profile so it doesn't fit properly to the ogive, ie : too big causing the bullet tip to contact in the seating stem first, or
2. is too narrow for the die, so there is space for it to wobble side to side in the die on seating

A few thou runout brought down to zero may not result in a measurable change if you can't shoot the difference.

 

[Bill Norris]

Before doing much else, remove the shell holder clip from your press and substitue an 'o' ring. Seat a bullet and see if there's any change in runout.

This was a huge help back years ago when I was looking at runout seriously. Don't pay it much mind anymore.

 

[charlie b]

I also had trouble with a Hornady seat die and my 6.5CM. Due to earlier issues with a Lee seat die and cast bullets, I had modified the seating stem and 'sleeved' the body. Worked well for cast so I tried it with the 6.5 and it worked out fairly well. Not near as good as my Redding competition dies, but, not near as expensive either

Had not heard of the clip/oring fix. Will do that tomorrow.

 

[L.Sherm]

If your worried about runout from seating dies go inline once you do you will never go back.

 

[jackieschmidt]

I use Redding Competition Seating Dies on everything.

Any seating die that does not completely encapsulate the case before the bullet contacts the seating stem is suspect.

 

[jpjulian]

I have dies by RCBS, Forster, Redding, & Hornady. They all produce good ammo with low to very low runout when set up correctly. By far, the lowest TIR of all of them are my Hornady dies. My Redding comp die has given me trouble with the heavier 77 grain .223 loads cracking the seating stem. With light bullets it's quite good. But if I want to load long for caliber bullets the Hornady dies give me the best TIR.

 

[tjtjwdad]

I'd get in touch with the die manufacturer and see what they say. It could be something that can be easily fixed or maybe they will just send you a new seating die.

 

[Straightshooter1]

Hi folks. To make a short story long, I've been rather unimpressed with the accuracy of my 6.5 prc. I won't name the maker until I get this all sorted out, but it's not a cheapo rifle. I've been struggling to get anything consistently under moa. After doing all the normal checks and even trying a different scope, I dug out my Sinclair concentricity gauge to check out my cartridges.

Lo and behold, I have some loaded rounds with .008-.010 tir runout. Fired cases are .001 or under on the necks, and my resized cases are .002 or under. For reference, I checked some Federal factory fusion loads that were .003 or under. That load shot reasonably well and easily beat most of my hand loads. Have I isolated the issue to the seating die, or is there something else I might be doing wrong? These are Hornady dies.

Also; Peterson brass out of the box has up to .004 runout at the neck. I'm guessing I should run them thru the sizer even though Peterson advises not to.

Sounds like it's time for a new and probably a different seating die.

If your worried about runout from seating dies go inline once you do you will never go back.

This ^^^^^

An L.E. Wilson inline seating die, with micro-adjustment, works really well for my 6.5 PRC.

 

[Jon Leary]

Before doing much else, remove the shell holder clip from your press and substitute an 'o' ring. Seat a bullet and see if there's any change in runout.

If you think that is causing runout just turn the shellholderso the open side is pointing at the clip.

 

[BoydAllen]

I would suggest that you base your evaluation of your seating die using cases that have been fired at least one time. When you FL size a fired case, what is the runout at the end of the neck? This runout is caused by the neck being at an angle to the centerline of the case body after sizing. seating a bullet will extend that angle so the farther out from the end of the neck the greater the total indicated runout. Once you have done all you can to reduce the runout of your sized brass, then you can evaluate whether the seater is making things worse, but understand that no seater can correct runout casused by crooked brass. They can make it worse. For example, I seated bullets in very straight (under .001 runout at the end of the neck) 6PPC cases using two different seaters. One was a Wilson, the other was a Hornady, The runout of the round produced with the Hornady die was twice what the runout of the round made using the Wilson die. Both were measured on their bullets, the same distance out from the end of the case neck.