Concentricity..Issues or me?

[Guest]

Ok..I've spent what I believe is the utmost care in prepping my (new) Lapua case 6.5-284 Cases. I ran the necks over and Sinclair Concentricity gauge and had .001-.002 runout on the necks if that! Now..Seating a few bullets in those cases I'm getting .003 on some and up to .006 on the others. I'm using a Redding Comp seater die and the proper shell holder.

Why am I getting this runout up to .006 on some cases and not others. The bullets are Sierra 142 gr HPBT match kings. None of the necks are turned and all were sized with a Redding Standard F/L die with expander ball.YUK I figured this was OK because of the low runout on the necks after sizing.

Any advise would be great. Let me know if I left out any important info


Oh..Neck thickness on all cases was right on the money with .001 or less vari.
Lab

 

[brian b]

Lablover,
It is the standard F/L die ,it over sizes your neck. get an S-die with a bushing or a comp die with a bushing and the problem most likely disappear.
B

 

[Guest]

Just as an test. I took one of the cases that was giving me grief. Pulled the bullet. Resized the case...Checked neck runout and got .001. Then checked thickness 001-002 vari. Reseated a bullet and got .005 runout on the bullet and .002 runout on the neck while the bullet was seated. Pulled the bullet again and then cleaned up the neck (turned to cut 75%) seated another bullet (new one) and now got .003 runout...Hmmmmmmmmmmm

Even those these cases show little runout and not much vari in thickness..Ya think I should turn the necks anyway? I thought with suck little neck runout that the neck turn cut would of cleaned the whole neck up...No sir ree bob! Just part of the neck

Joe

 

[dcb]

redding only gurantees there fl die with and expander to size
.003" run out! .003" to .007 is fairly common.
I would fire form the cases first before i started carvin on them.
I have switched over to collet dies. with win brass necks cleaned up to 60/70% run out is less than .0015"

 

[Mysticplayer]

Sounds like the seating die plunger is not bearing evenly on the ogive of your bullets. This forces the bullets crooked when seated. NO good.

Deepen the cavity in the plunger. Doesn't matter what you use. Just make sure that the tip is not bottoming out first. I would just take a Dremel to it. A drill might not be hard enough.

With this done, the bullet will now only contact the base of the plunger at the ogive. Way more consistent and usually solves seating runout issues. Of course, you can switch to another die if this persists as something else is hanging up.

Jerry

 

[Guest]

Jerry

Checked that and am getting no contact on nose of bullet. I really think is the necks

 

[D.P.]

Lab
I think brian b hit it. My 6.5 and 300WSM did the same thing. The FL die sized the sh-- out of the brass. The bushing solved my problem. With virgin brass, before the neck bushing came I had better results just running the ball through. 1/2 the runout as FL

 

[Guest]

I think your right. Got the right bushing in the mail my way so I can try that. Tight now I only have bushings if I neck turn. I will say...The few cases I neck turned and resized..Then seated..The problem was .002 or less.

Thanks

Joe

 

[WildRose]

Ok..I've spent what I believe is the utmost care in prepping my (new) Lapua case 6.5-284 Cases. I ran the necks over and Sinclair Concentricity gauge and had .001-.002 runout on the necks if that! Now..Seating a few bullets in those cases I'm getting .003 on some and up to .006 on the others. I'm using a Redding Comp seater die and the proper shell holder.

Why am I getting this runout up to .006 on some cases and not others. The bullets are Sierra 142 gr HPBT match kings. None of the necks are turned and all were sized with a Redding Standard F/L die with expander ball.YUK I figured this was OK because of the low runout on the necks after sizing.

Any advise would be great. Let me know if I left out any important info


Oh..Neck thickness on all cases was right on the money with .001 or less vari.
Lab

You are compacting the same brass that gave a proper neck size for a 7mm, to 6.5mm. That brass doesn't go away.

You will probably either have to get a neck reem at 6.5mm or turn them after resizing in order to get a consistent neck diameter after loading.

Depending on your chamber this excess brass may very well create a dangerous over pressure situation so be very leery of firing those that are showing the .003 over size.

 

[Gene]

Neck consistency is a bugaboo for many of us. I can accept .003" or less. If more than that, I cull out the excesses and use them for sighters.

First of all, brass must be fired once or twice to fit the chamber. Good bushing type sizer and micrometer seater dies are a must. The seater die ogive cup must be deep enough so that the meplats do not touch. I put a touch of Prussian blue on a bullet tip to find out whether there is contact. Necks must be first turned. Even sizer bushings can be faulty. Try this: Size the case once, then turn it 180 degrees in the shell holder and size it again. Do same with the seater; lower the bullet about 70%, turn in the shell holder and lower it to desired OAL. Theory is that increases consistency all around. I have no way to prove this theory.

 

[RDM416]

.

Try this: Size the case once, then turn it 180 degrees in the shell holder and size it again. Do same with the seater; lower the bullet about 70%, turn in the shell holder and lower it to desired OAL. Theory is that increases consistency all around. I have no way to prove this theory.

+1 on this. I go a little further though. When sizing I will lift the ram just enough to free the case and rotate the case about 1/4 turn 4 or 5 times bringing the ram back down each time. I do the same for seating a bullet.

I have proved this works many times by measuring runout on rounds I loaded with this method and rounds loaded with one sizing and seating stroke. Using this method I get my rounds ALL within .003 with the vast majority .001 or less. If I occasionally get a .004 I can usually put it back in the seater and bring the ram down 8 or 10 times rotating it just a little each time and bring it to .003 or less. This is with a long 338 Khan, shorter cases should work even better.

One other thing is I do not use an expander ball. They tend to put stress on the neck / shoulder when pulled out.

 

[J E Custom]

As a matter of routine I size "New" brass with the turning sizer from Sinclair and then turn all necks
the same before ant load sizing is done.

This seems to start the brass out concentric before any loading or firing can permanently
shape them out of concentric.

If I start sizing before turning the neck thickness difference seams to move it to the thinner side
throwing it off center more.

It seems even more important to do this if I am sizing down a case from a larger parent case.

It will not eliminate the problem but it does help to minimize it.

J E CUSTOM

 

[Mikecr]

I ran the necks over and Sinclair Concentricity gauge

Which 'concentricity' gauge are you using?

None of the necks are turned and all were sized with a Redding Standard F/L die with expander ball

Not the easiest path to low runout.

Neck thickness on all cases was right on the money with .001 or less vari

How did you measure this?

It 'seems' most like a seating issue, but I wonder about the above first.

 

[learning]

The origanal post was in 05.