Concentricity problem 308 winchester

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hamel_22

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I am become frustrated. When I check for neck run-out on fired case, it is alway 0.0015 or less. After being necksized or full lenght sized, it sometime become like 0.003 or 0.004 which is bad as far as I know. Some of my case go out ok but I would say that 20-30% of them seemed to ruined by the process.

My press is a RCBS ruckchucker and my dies are the Redding competition set. I have also used the FL serie S from Redding and the results were the same.

My reloading steps are as follow.

1- Lube and FL sizing (which is what I prefer since I want those bullet to fit properly at all time)
2- Tumbling for 2 hours in media
3- Trim if needed
4- Priming
5- Charging the powder
6- Bullet seating
 
Why FL size if you have a competition neck size die? Try neck sizing then give the case a 1/4 turn and run it through again. Maybe try a different shell holder? Remember .003" run out is really +/-.0015. Is your brass neck turned and what type of brass are you using?
 
Should have asked this before. Have you chamfered the inside of the case mouth and deburred the outside?
"...seemed to ruined..." They're not.
 
Yes I chamfered them. But the big amount of run-out appear right after the sizing process when I ckeck them with my RCBS Case Master.

I'm thinking that the press is out of alignment but how can I verify this?
 
If you are using an expanding "button" with your sizing die, make sure it is perfectly centered in your sizing die. That stinking button can produce the excess runout you describe. I had the same issue with a 6.5x55 AI die set, and once I centered the expander button properly, Voila! the runout disappeared entirely (.0005" or less) Regards, Eagleye.
 
Tell me if I'm wrong but I heard that carbide bushing didn't need lube to functon properly.

I've try to lube the necks on 5 cases so far and the neck run-out seem to have dropped down to 0.002 max.

Is this OK or it is just a coincidence?
 
Always LUBE the necks, inside and out. Use a wax based lube and tumble it off afterward.

Dump the neck expander button, get a Sinclair Mandrel die:
http://www.sinclairintl.com/cgi-bin/category.cgi?category=search&item=NT-EXP&type=store
The regular mandrel is 0.306" and the oversized one is 0.307".

The neck expander button pulls on the neck on the way out (whereas the mandrel opens them on the way down) if you aren't using lube, stuff is sticking and its probably pulling them out of shape. Also, make sure to clean the insides of the necks really well. I brush them with an oversized brush before my first tubling and remove the dust afterward with a bore swab before sizing.

Sizing brass shouldn't sound like opening a barn door.
 
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hamel_22 said:
Some of my case go out ok but I would say that 20-30% of them seemed to ruined by the process.
Click to expand...

Check the inside of your necks. If you aren't using lube, you MAY end up with buildup on the expander button that will end up scratching the hell out of the inside of the case necks and giving you erratic pressures and velocities.
 
To isolate when the runout occurs, you need to check the runout after each stage of the loading process. If you are neck sizing only and you are using a bushing die set, I don't bother to lube the case neck. If you use the body die, you will need to use something like Imperial Sizing Wax, but you don't need much, and you should only use it to bump the shoulder back a small amount. If your die set uses an expander button, you should dip the case neck in powdered graphite.

Once you have determined when in the process the runout occurs, you can then take steps to correct it. Don't consider the cases with excessive runout ruined, just keep them aside for practice sessions rather than competition. After they have been fired they will return to minimal runout, provided that they were concentric to start with.

A rubber "O" ring under the lock ring of the bullet seater stem, or of the expander button stem can help center either. I also got rid of the retaining spring that holds the shell holder to the ram and replaced it with an "O" ring so the shell holder can find it's own center under the die, but because it moves freely under the die, you must watch that it is not badly out of alignment as the case enters the die.
 
hamel_22 said:
Tell me if I'm wrong but I heard that carbide bushing didn't need lube to functon properly.
Click to expand...

With a carbide bushing, outside lube is a waste of time. Your redding dies will also accept a carbide expander, making inside lube also a waste of time. Having said that, with neck-turned brass and the right bushing you don't need the expander at all.
 
Boomer said:
To isolate when the runout occurs, you need to check the runout after each stage of the loading process.
Click to expand...

X2 for me. It looked from the first post like runout was being tested before and after sizing the case, but I wasn't completely sure.
One thing I found I can do if runout on a loaded case is above 1 thou is to adjust the bullet a bit by pushing on it at the point of highest runout. I hold the case in my hand and pushed a bit on it a bit with my thumb to straighten it out, then recheck the runout. I wont say I get all the reloads under a thou but I usually can with most of them. The others I use for shooting in etc. Another thing that old shooters used to do - Heck maybe they still do! - was index cases after reloading at the spot where the runout was highest. They would then chamber the cases consistently with the high spot up or down in the chamber. It's better to have a system that does things straight, of course, but I understand this was one trick used in competitions where you couldn't make your own bullets. :) fred
 
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Try this method maybe?

I use the Lee collett neck sizing die, exclusively, I have a Redding bushing neck die and found that the Lee makes straighter ammo, if I full length the brass I use the Redding body die afterwards. Collett die = no sizing lube which is nice. Only full length when getting tight to chamber. my $.02
:)
 
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