Neck Turning

[Russell3812]

After doing some reading I purchased a K&M neck turning tool. I also bought a Sinclair Concentricity Gauge. The neck turning tool came last week and I turned 50 pieces of new brass. Went to the range this weekend shot the loaded rounds and all went well. The Sinclair Concentricity gauge came today and I ran the fireformed brass over it. Runout measured no more than .001 or .002".
Happy with my successful first run I started with another fresh batch of virgin, Winchester .308 brass. Measuring it on the gauge I found runout varying from .005" to .007" Started with the neck turning tool and turned 4 or 5 pieces. Not only did they still indicate the same amount of runout but now it appears that there was more! brass with .005" went to .007" and .007" to .010" Holy crap!
One of two things I can gather from this.

1) I'm doing something terribly wrong either during the turning process or in using the Sinclair gauge.

2) Once the brass is fireformed then it's time to use the concentricity gauge. As I mentioned, the fireformed brass had .001" - .002" of runout.

Please give me your thoughts as to what may be the problem if any. Thank you.

 

[BK7saum]

Re: Neck Turning

Did you full length size the new brass without the expander ball and then expand with a mandrel before neck turning?

Full length size the new neck turned cases, expand with a mandrel, and then measure your runout. I would think that the runout should decrease dramatically.

Resizing using the expander ball is supposed to be notorious for causing runout in the case neck as it is pulled/dragged back through the neck.

Hope you get it figured out.

 

[wilecoyote]

Re: Neck Turning

I don't believe in the perfect uniformity of new brass, no matter the brand _I prefer fully resize the new brass first,anyway_ after that I can think about a first light neck turning,followed by the firt shooting_ sometimes I'm lucky, (...sometimes)

 

[Russell3812]

Re: Neck Turning

Ran through full length sizing die, used expander mandrel. Still measuring close to .007" of runout on the new brass..

It's strange how every one of the fireformed pieces is almost perfect. Again measuring .001 to .002.

Can't understand how after neck turning new brass there's no change in runout. It's cutting the brass but when placed on the sinclair gauge it shows the same as if I didn't do a thing to it.

 

[wilecoyote]

Re: Neck Turning

can be the unfired brass body has some springback,nothwithstanting the full res,,etc._ anyway,you have in some way uniformed the necks and, after the first shooting, the fireforming "print" the dimension of your rifle chamber on the brass_this "printing"is really hard,under huge heat and pressure:after that the outside of the brass has,more or less,the dimension of the chamber,while any imperfection of the body (runout) is pushed,and hided, inside the body,where simply you can't measure or see_

 

[flashhole]

Re: Neck Turning

If the centerline of the neck is off center to the centerline of the case, neck turning will uniform the neck thickness but will not change runout. Neck turning is to make the necks uniform in thickness and the biggest benefit is equal neck tension on the bullet.

Curious, why do you think neck turning will reduce runout if the neck is off center to begin with?

Take the 5 worst pieces you have, load them and shoot them, then check for runout again. It is likely your chamber is cut accurately and fire forming will negate runout to the extent the chamber is precisely cut.

You're doing the right things by poking and asking questions. Just remember what the results are telling you to improve your process. I assume you have the K&M expand iron to size the neck before turning.

You might also try this. Take a case that is known low runout, lube it, and use it to align your sizing die to the press before locking the die in place. Take a case that is known high runout and resize it in the die and check for runout again. Runout should be reduced to the extent the "master" case aligned the die.

Little tricks like polishing the expander ball and cleaning the inside of the case neck to reduce friction help too. Your concentricity gage will point you in the right direction to reduce runout in the processing steps.

 

[Russell3812]

Re: Neck Turning

alright I can buy that answer. Gonna load up some of this new brass and see if I get the same results the next time. Thanks for your input.

 

[Russell3812]

Re: Neck Turning

flashole,

Maybe I wasn't clear. The runout in the cases mentioned existed before and after resizing the brass. I don't believe the process of resizing caused the runout. This existed before I touched it....straight out the bag.

After resizing and neck turning this condition still exists.

 

[Russell3812]

Re: Neck Turning

I think I understand you're saying though..... so the brass could be screwed to begin with. After it fireforms to the chamber it corrects the alignment of the neck with the center of the casing itself.... i think that's what you're telling me.

 

[wilecoyote]

Re: Neck Turning

...we must remember the the imperfections removed turning the necks are only the last,and smaller/thinner,portion of a mayor imperfection of the brass,running all the way from the neck down,and more "down"we go,bigger is the imperfection_ That's the reason because we spend more money on the "better" brass:because we hope that Lapua,Sako,etc.,being more expensive,can guarantee us a better uniformity,outside,inside,and eveywhere_sometime,as I have sayed,we are lucky.._I stop here,because at this point I ever have the the idea that for me it's no more science,but faith in Odin (please,forgive my "venitian" english grammar_)

 

[wilecoyote]

Re: Neck Turning

...yes

 

[Russell3812]

Re: Neck Turning

ha ha... no worries coyote. I understand you fine. I have some Lapua brass and been playing around with that tonight using the Sinclair Gauge as well. Noticing a big difference. But that stuff is crazy expensive. If you had your choice what would you buy.... Norma, Lapua or Sako?

 

[wilecoyote]

Re: Neck Turning

1Sako_2Lapua_3Norma (more Odin than Werner Von Braun)_ But I have seen people fireforming from a bench,keeping the brass who send the bullets in the same hole for the real business, and the rest as practice brass: this is really faith in the science (more Werner Von Braun than Odin)_ Good luck!

 

[Russell3812]

Re: Neck Turning

Im gonna have to look up this Oden you speak of

 

[wilecoyote]

Re: Neck Turning

...you can't mistake:it's the only black-patch,one-eyed in all the Valhalla (bad temper,too)_