Concentricity Problems

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jugi16

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I am loading for my 1000 yard 308 rig at the moment and have a problem with bullet run out on my loads. I can't get any better than .003", most loaded rounds are running in the .002" range with the Redding Comp S bushing dies I'm using. I am using Lapua brass that I neck turn with a Sinclair tool. I usually take .0005" off the necks as Lapua is pretty good right out of the box. I fire formed my cases and they show .0005-.0075" run out on the neck of the brass.

I can't figure out what I am doing wrong from the time I resize the neck to seat the bullet that would throw things out .003". I have the bushing loose in the shell holder so it can float (I size 1/2 of the neck). I've taken apart and cleaned the bushing die and bullet seating die.....everything looks good.

Anyone have any recomendations? Are there better dies out there than the Redding Comp S that might solve this? Am I not doing somthing right?
 
runout

a mutitude of things will cause runout, most common is the shellholder it self,
I used to use RCBS or Lee good enough for hunting loads where a little runout does not matter but once you get into precission shooting it's huge
also I never had any luck keeping those bushings loose in the die, I measure until I find a brass that has the least runout, .0002 or less, I insert that into the die and finger tight plug on bushing, try to keep everything the same, Redding,Redding and Redding, or what ever brand you use, next it could be your press, do you have alot of free play in the ram? if you think your press is good,you can confirm the shellholder by checking the runout on the brass before and after sizing, if you think your shell holder is good, try a differant press, several out there are good, but for precission reloading, look at what the benchrest shooters use for equipment

regards, Grant



jugi16 said:
I am loading for my 1000 yard 308 rig at the moment and have a problem with bullet run out on my loads. I can't get any better than .003", most loaded rounds are running in the .002" range with the Redding Comp S bushing dies I'm using. I am using Lapua brass that I neck turn with a Sinclair tool. I usually take .0005" off the necks as Lapua is pretty good right out of the box. I fire formed my cases and they show .0005-.0075" run out on the neck of the brass.

I can't figure out what I am doing wrong from the time I resize the neck to seat the bullet that would throw things out .003". I have the bushing loose in the shell holder so it can float (I size 1/2 of the neck). I've taken apart and cleaned the bushing die and bullet seating die.....everything looks good.

Anyone have any recomendations? Are there better dies out there than the Redding Comp S that might solve this? Am I not doing somthing right?
Click to expand...
 
A few questions.

1) Where are you measuring the bullet run-out? Just in front of the neck or at the tip?

2) What is your neck run-out after you size the neck but before you attempt to seat the bullet?

3) What seating die do you use?

4) What tool do you use to measure run-out?
 
Instead of wondering what is "wrong" with your ammo on a bench-top dial, why not try shooting it for group. Just cause it shows a bit of runout doesn't mean it won't shoot.

A bunch of years ago I spent some time sorting ammo by runout and then shot everything for group. I had a pile of ammo that was everything that had the worst runout. Guess what, the stuff that showed the worst runout grouped better than the stuff with near zero runout.

After that I stopped worrying about it.
 
1) Where are you measuring the bullet run-out? Just in front of the neck or at the tip?


Just in front of the neck.



2) What is your neck run-out after you size the neck but before you attempt to seat the bullet?

0 run out after I measure a fired case on the neck. 1-3 thou after I resize the neck with the redding bushing.



3) What seating die do you use?

Redding Match S type seater and Redding Match S type neck die with the titanium bushings. RCBS Shelholder and brand new RCBS single stage chucker supreme. Lapua Brass 175 SMK's



4) What tool do you use to measure run-out?

RCBS Case master
__________________
 
jugi16 said:
0 run out after I measure a fired case on the neck. 1-3 thou after I resize the neck with the redding bushing.
Click to expand...

There's your issue.

Try a different set of sizing dies.

If you have a standard full-length die try removing the expander ball and size the cases for a crush fit in your rifle chamber. After all the cases are sized replace the expander ball and run the cases into the die again just enough to push the ball through the neck and not touch the case body. Check for run-out.
 
Well isn't that the purpose of the Redding Type S bushing kit to resize the neck only and have no run out? I don't use an expander ball on my dies I am trying to keep the neck work to a minimum for case life.
 
Make sure that the bushing has a little bit of movement - the Redding instructions explain it well ... but I see that you are doing that by your post. Keeping the die a 'bit loose' while you size a round, then tighten the die with the ram fully up may help.

How much tension are you putting on the neck (which bushing, plus the wall thickness of your case necks)?
 
Run out

Some of the run out you can't get away from. When you neck size the brass,it will compress where the least restriction is "in the neck in the thinnest area" so this reduction is not concentric and gives you an added bit of run out. Don't let it drive you nuts, at the range it may shoot great.
Bill
 
'Boo said:
There's your issue.

Try a different set of sizing dies.
Click to expand...
Not necessarily, since imperfectly-made brass will come out crooked from perfectly-straight dies.

To find out if it is the dies, put a mark on the brass rim before sizing, then index the mark to face you when sizing. If it is the dies, peak runout will be in a consistent location in relation to the mark. If it is the brass, peak runout will not be related to the position of the mark.
 
Lets start at the beginning. Are your case necks a uniform thickness? This is the first thing to address, and if out by more than .004 they should be turned before you can achieve the accuracy potential of your rifle. Next take a brass case with a uniform neck thickness that has been fired but not resized and check the runout. If it has an excess of .002, you have a chamber problem. If not, resize it and check the runout. If it exceeds .004, you have a sizing die problem; either it is not set up properly, it is not cut to industry standards, or you need a different bushing. If you are within .002 seat your bullet and check the runout. If it exceeds .002 the culprit can be the seating die, the seating die set up, or an out of round bullet.
 
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