Newby neck turn question

[acssa]

Good day to all, Please excuse my questions and comments, I dont mean to upset anyone.

I got some new Lapua brass with more than .004+ neck runout. I was told to neck turn them but that did not help much.

I noticed that some brass necks in general vary in neck case wall thickness... so I understand why neck turning are done to even that thickness. I also checked the run out on new brass cases, and some S&B cases were only out by less than .001, I also think that forming the brass in a quality die tool, results in the outside area/shape forming of the case, but does not do much for the inside area/shape(it is shaped relative to what happens on the outside.. Taking into calculation that wall thickness can vary you see that the bullet will be off centre/ have run out.

Is it then not better to neck turn on the inside of the neck? Why do people turn the outside of the neck if it result in a bigger bullet run out?

 

[stgw77]

Do not worry about runout on new brass...just do neck turning, load them and fire them...full pressure load will straighten them just fine...

 

['Freak]

Howdy,
New to neck turning myself but best I recall if it’s new never fired brass you neck size but without an expander to true the outside of the neck and you’ll be pushing all the funky to the inside. Then you run it over the expander mandrel of your neck turn tool set so truing the inside of the neck leaving it the right diameter for the correct tight fit on the turning mandrel and you’ll be pushing all the funky back to the outside surface of the neck where you can have at it. You’ll skin off much of if not all of the thicker areas and irregularities while doing the neck turning depending on your final neck wall thickness. If I’m way wrong hopefully somebody will jump in and fix us both.

'Freak

 

[Joe R]

OleFreak said:
Howdy,
New to neck turning myself but best I recall if it’s new never fired brass you neck size but without an expander to true the outside of the neck and you’ll be pushing all the funky to the inside. Then you run it over the expander mandrel of your neck turn tool set so truing the inside of the neck leaving it the right diameter for the correct tight fit on the turning mandrel and you’ll be pushing all the funky back to the outside surface of the neck where you can have at it. You’ll skin off much of if not all of the thicker areas and irregularities while doing the neck turning depending on your final neck wall thickness. If I’m way wrong hopefully somebody will jump in and fix us both.

'Freak

You got it right OleFreak.

 

['Freak]

OleFreak said:
Howdy,
New to neck turning myself but best I recall if it’s new never fired brass you neck size but without an expander to true the outside of the neck and you’ll be pushing all the funky to the inside. Then you run it over the expander mandrel of your neck turn tool set so truing the inside of the neck leaving it the right diameter for the correct tight fit on the turning mandrel and you’ll be pushing all the funky back to the outside surface of the neck where you can have at it. You’ll skin off much of if not all of the thicker areas and irregularities while doing the neck turning depending on your final neck wall thickness. If I’m way wrong hopefully somebody will jump in and fix us both.

'Freak

You got it right OleFreak.

Good to see confirmation, Joe R. I’ve been trying to absorb the good stuff from a number of sources including a Glen Zediker book on loading for competition, across the course specifically, but a plenty still applies for what I like to do to entertain myself.

‘Freak

 

[oklahomaboy]

OleFreak is correct in that you have to run your re-sized brass over the correct expander to prepare it for turning. However, some study of a batch of your new cases is required to determine how much of the diameter needs to removed. It is not required to perform a 100% cut around the neck. In a hunting rifle, a difference in thickness from one side of the case to the other of .0005 is acceptable. In fact, if all cases in a batch (you decide how many constitutes a batch) were within .001, you likely won't see results from neck turning. Target rifles capable of better accuracy may respond to turning off the thickness differential to about .0002 or so. Further, the more you thin the necks, the more sizing is required from the fired case diameter to the sized diameter. Excessive sizing can lead to more run-out in your case necks. Resulting excessive sizing reduces case life.

 

['Freak]

It’s likely I’ll have to settle for just a neck cleanup, turning off only the worst of thicker neck wall areas. Mine are all still with their OEM chamber so I need to keep finished neck size on up there.

‘Freak