runout created by bullet seating

[ShtrRdy]

Are you using a Chamber Type of bullet seating die? Like the Redding or Forster Competition die?

 

[bigedp51]

Redding S type bushing die. The brass comes out straight...

The Redding bushing die FAQ tell you if the neck thickness varies .002 or more to use the expander that comes with the bushing die. You will need a bushing .002 smaller when using the expander. Meaning push the neck irregularities to the outside of the neck.

When using a bushing die without the expander a uniform case neck will have very low case neck runout and very low bullet runout. A non-uniform case neck will have very low case neck runout BUT bullet runout will be higher. Meaning the seated bullet will not be centered with the center line of the case body and have increased bullet runout.

I use Forster full length non-bushing dies with the expander and then subtract the neck thickness variations from the case neck runout after sizing.

Bottom line, if you do not neck turn you are better off using a standard die with a expander.

Many reloaders use a body die and the Lee collet neck sizing die because the get less runout than with bushing dies. I prefer the Forster full length benchrest dies with their high mounted floating expander that greatly reduces neck runout. And I also use the Forster inline benchrest seating dies.

I use the Redding neck thickness gauge below to sort brass if not neck turning. And as a example if the case has .003 neck thickness variations I subtract that from my total case neck runout after sizing. After loading and bullet seating I want the bullet runout to be as close as possible to what the corrected case neck runout was.

 

[clownbuster]

Ok, so there is "runout" and "total indicated runout"... Which number are you providing? If your seeing .005" total indicated runout than your actual runout is .0025" (One half your TIR). A lot of people get this messed up. You have to cut your TIR number in half to get your actual runout number.... Now, with that said, TIR is still a good measurement of round to round concentricity... But, your setup isnt putting out .005" runout either. Its putting out a max of .0025" and something in your process is causing this. Anything under .005" runout is actual just fine. Sure, we all want the .001 runout number but anything under .005" is good to go.

My setup. Forster Co-Ax, Forster FL sizing die honed to size neck .004" under final sized neck diameter with expander removed. I set final neck tension with a 21st Century TiN turning mandrel for a final neck diameter of .002" neck tension. My runout is consistently in the 0.0005"-0.0015" TIR range meaning my actual runout is half those numbers. I also anneal every 3rd firing on Lapua brass.


So, a few questions...

1) Did you ream the brass as a last step just before seating? If yes, did you again measure your run out prior to seating? Brass is soft and "springy", even softer when its thin, and susceptible to deformation. Dont expect your brass to hold uniformity directly after reaming the mouth out. It will likely be better on your next sizing.
2) Are you annealing? If so, how often?
3) How many firings on that brass?
4) Have you sized a case with your sizing die then measured the runout on the neck? Take the average of 5 cases. What is your actual runout? (Half your TIR)
5) Measure runout right at the ogive of the bullet where it contacts the lands. Whats your actual runout there?

I am pretty positive you will find your cause following the above steps but honestly your setup is producing pretty straight ammo already. If you told me your actual runout was .009" and not your TIR than I would be concerned. I suspect your giving us your TIR.....

 

[clownbuster]

Maybe you mentioned this before, but I'll ask anyways:
Are you locking down your sizing die and seating die tight to the press (not recommended), or do you run a thin rubber o-ring under the lock ring and just snug the lock ring allowing the dies to "float"? (recommended)
Are you running a VLD seating stem (recommended) in your seating die or the standard one that came with it? (Not recommended)

 

[GW Hunter]

Thanks for all the responses. It obvious to me that I need to begin turning the necks on my brass to take it to the next level. I understand how the case neck can straight with the body and if the necks walls are off than the bullet will be off center. As far as whether the runout is TIR or not... I use a sinclair gauge. Whether that is considered runout or TIR, I'm still not sure. I need to read up on that...

 

[redleg1013]

Oh for Pete's sake didn't we just cover this like two weeks ago?

Learn to use the search bar folks.

https://www.longrangehunting.com/threads/reading-a-sinclair-concentricity-gauge.218885/

 

[jepp2]

"I use a sinclair gauge. Whether that is considered runout or TIR, I'm still not sure. I need to read up on that..."

If you are reporting the total movement of the needle, that is TIR. If you are reporting the swing to one side, the is runout.

 

[GW Hunter]

"I use a sinclair gauge. Whether that is considered runout or TIR, I'm still not sure. I need to read up on that..."

If you are reporting the total movement of the needle, that is TIR. If you are reporting the swing to one side, the is runout.

I'm not sure how to answer that. I place the case in the block and start rotating. Invariably the needle will swing one way until it stops and then swing back until it stops and swings back. Depending on where the gauge starts to measure, the swing to one side is not necessarily the same amount as the swing to the other. I guess the entire travel of the needle is TIR?

 

[jepp2]

I guess the entire travel of the needle is TIR?

Yes. Divide by 2 for runout.

And by the way, I spent a lot of time working to reduce case neck runout during sizing. I now hone my die necks to the diameter I want. I have used Redding Competition bullet seating dies, so I always just "assumed" bullets were seated straight. Nope. Now I seat in 3 steps rotating the case about 120 degrees and reduced my bullet runout by 50%.

 

[clownbuster]

I'm not sure how to answer that. I place the case in the block and start rotating. Invariably the needle will swing one way until it stops and then swing back until it stops and swings back. Depending on where the gauge starts to measure, the swing to one side is not necessarily the same amount as the swing to the other. I guess the entire travel of the needle is TIR?

Correct

 

[GW Hunter]

Ok... The numbers are TIR. That is the value of half of the rotation of the case. .005 in the worst of them. .005 in one direction and then .005 in the other

 

[GW Hunter]

Obviously .000 is what we all shoot for. With the value given of <.002 being the acceptable number, is that for TIR or runout?

 

[GW Hunter]

Oh for Pete's sake didn't we just cover this like two weeks ago?

Learn to use the search bar folks.

https://www.longrangehunting.com/threads/reading-a-sinclair-concentricity-gauge.218885/

Well it didn't start here....

 

[clownbuster]

Obviously .000 is what we all shoot for. With the value given of <.002 being the acceptable number, is that for TIR or runout?

In my studies and experience, a max of 0.005 TIR is fine. You'll drive yourself nuts if 0.002 is the acceptable standard. I know, I did and spent alot of time and money getting there. There was almost no measurable difference @ 1000 yards between loads producing 0.005 TIR and my loads producing 0.0005.