Neck Turning New Brass

Would it be ok to neck turn unfired brass that has a neck runout of around .003-.005? The neck wall thickness varies by as much as .0015 on some cases. My concern is that the cutter will be removing too much brass because the neck isn't concentric. But maybe the neck turning pilot will keep things centered? I could fire form them before I neck turn but I'm running a bushing die and don't really want to have to run them over an expander ball again and induce runout thus having to fireform all 50 again before I can get really concentric ammo for load development. I appreciate your thoughts.

New brass should already have sized down necks. Simply use a correct sized expander mandrel to open necks to the correct size for the cutter mandrel. That should push the irregularities to the outside of the necks for easy removal.
I bought most of my turning tools and various mandrels from Sinclair Inter. if that helps.

Varmint Hunter said:

New brass should already have sized down necks. Simply use a correct sized expander mandrel to open necks to the correct size for the cutter mandrel. That should push the irregularities to the outside of the necks for easy removal.
I bought most of my turning tools and various mandrels from Sinclair Inter. if that helps.

Click to expand...

Yeah that makes sense, I guess my question is that all things being equal if I have two pieces of unfired brass both of which have .0015 neck wall variance but one round has .005 runout and the other has .001 runout wouldn't the cutter cut way too much brass off the "high side" of the piece with .005 runout? I may be overthinking this but getting a concentricity tool really opened my eyes to a lot of issues that were out of sight out of mind before.

Is this what you are worried about?



Turning new brass will not necessarily mean you will have a concentric load.

But, theoretically, firing that case in a concentric chamber will move the neck over to align with the case body and subsequent loads will improve (at least does for me)

The biggest problem is if the thick and thin brass extends down into the case body and causes banana shaping which will again screw up your concentricity

I prefer to turn new cases, unless I'm necking up or down to form brass. If your sizing mandrel is a good fit to the turning mandrel, you should have very little variance. Heat and poor technique would cause more variance.

On this subject...what neck turning tool/setup is the best? My hornady model plays absolute HELL trying to get the case locked down straight enough that it doesn't excessively wobble.

I use only K&M turners and tools. 21st Century makes a good tool, also.

Don't concern yourself with runout, or attempt to control 'wobble' during neck turning.
Just achieve a good mandrel fit and allow the cutter body to float in your hand. You'll end up with great thickness consistency.
Then when you fireform the brass, runout will nearly disappear.

The Forster Hot 100 is not a bad choice



It has a wide cutter which makes for a smoother cut



And you can buy a reamer (.003" over caliber) later if your gun is set up with the right neck dimension



The K&M has a cutter that is narrow, hard to get a smooth cut and the reamer mandrel also has the cutter on the very end and is narrow so it will severely booger up the inside of the neck. Also relatively more expensive.

But that being said the K&M is an excellent tool and has more options

have one Lee 30-06 die that no matter how I adjust it, play with the spindle, the run out is horrible. My Lee .223 and 308 die were excellent.

Still there maybe an aggravating factor, and that is case lube.

I lube the inside of my case necks then tumble my brass, in a can, with a patch saturated with RCBS water soluble case lube. It is an easy way to lube 100 or 200 cases. However the entire case is coated in lube. Sometimes more lube, sometimes less.

I measured case neck run out after sizing, those cases which I had wiped the case lube off the neck/shoulder before sizing had greatly reduced case neck run out. I don't know why, but it seems to work for my dies. I have Lyman small base, and RCBS small base, and this also worked with the Lee dies in 223 and 308.

Mikecr said:

Don't concern yourself with runout, or attempt to control 'wobble' during neck turning.
Just achieve a good mandrel fit and allow the cutter body to float in your hand. You'll end up with great thickness consistency.
Then when you fireform the brass, runout will nearly disappear.

Click to expand...

Thanks, that was what I was wondering about.

I normally work on 50 cases at a time so I can measure all of them and find the case neck that measures the least thickness. That measurement will give me an idea on how thin my case necks will end up when turned. I use Lapua brass, so, my cases have never ended up less than .013 when done. Using an expander mandrel on all the cases should get them about as concentric as they are going to get. I've never had a problem using this method.