Neck turning question

[Whitshot]

I'm brand new to neck turning, and was hoping someone could sort conflicting reaserch for me. I'm using Hornady and Starline 6.5 Creedmoor. My setup is a PMC Tool cutter. My questions are

1. What is minimum neck tension? I've heard .002.
Is .0015 enough or better?
Is .0025 to tight?
I'm using these for target shooting and they are not getting knocked around or carried loose.

2. What neck thickness is ok? I'm at .010 right now but that leaves a slight patch of the neck untouched by the cutter. Should I cut another .001-.003 more? or is keeping some "meat" or thickness in the necks more important for case life?

Thanks guys

 

[spife7980]

1. What is minimum neck tension? I've heard .002.
Is .0015 enough or better?
Is .0025 to tight?
I'm using these for target shooting and they are not getting knocked around or carried loose.
This depends on where your particular rifle and brass combos shoots best. We cant tell you what yours does best, only you can test that. Some people use .004" of interference fit, some people use .0005 and do whats called soft seating.

2. What neck thickness is ok? I'm at .010 right now but that leaves a slight patch of the neck untouched by the cutter. Should I cut another .001-.003 more? or is keeping some "meat" or thickness in the necks more important for case life?
Again, this depends. Do you know how large your chamber neck is? The more you turn off the brass the further they will expand on each firing. Just so long as you have a minimum of .003-4 of clearance for a field rifle youll be alright, you dont want less than that as a grain of sand getting in there could lock you up.

I included some comments above inside this quote in red
The actual tension used is a product of the many variables. http://www.accurateshooter.com/technical-articles/reloading/neck-tension-not-just-bushing-size/
An interference fit of .002 for one brass could impart 2x as much force on the bullet as .002 of fit with another type of brass depending on particulars.
A thinner neck will require more of an interference fit to make the same amount of tension as a thicker neck would.
A lubed neck will require more of an interference fit than a dry neck will
Lots of variables and so many that its really tough to say one way or the other scientifically short of testing it yourself.

Typically people like .002 of a difference between sized and loaded round diameter as it seems like a decent baseline rule of thumb but it is by no means ideal for any.

Turning your brass to adjust the amount neck tension is putting the cart before the horse. Turning is used to equalize the neck thickness in the individual neck, removing the high spots. Using a different bushing would be the method to adjust how much tension those clean necks put on the brass.

Before you go cleaning up those necks anymore figure out how much extra room around them you have already. .010 is getting on the thin side for a creed neck. Being a creed I doubt your set up requires neck turning at all from a functionality stand point.

 

[shoot4fun]

SAAMI neck diameter is in the order of .296 and (using .014 as neck thickness) your loaded unturned ammo should be measuring somewhere around .291 or .292 neck diameter. At that you have approximately .004 neck clearance for expansion during firing. When necks are turned to .010 that increases the clearance by around .008 and you have around .012 clearance. IMHO that is too much and having too much clearance is just as much a detraction from accuracy potential as having too much/too little neck tension. Case necks for SAAMI chambers do not need to be turned to be accurate. The use of the expander ball in your sizing die or a Lee Collet Die should push any imperfections to the outside of the neck and uniform neck tension can be attained without turning. If you don't like the drag from the bushing then use Imperial Dry Lube on the inside of the necks.
Unless you have bushing dies you will not be able to size the necks to get any neck tension at all. If you do have bushing dies try bushings in .281 and .282
As far as proper neck tension goes, the only way to know is test for what is best in your rifle.

 

[ZiaHunter]

.010 neck wall thickness is pretty thin and generally try to stay in the .013 range. My Dasher has a tight neck and turn to .012. Generally try to maintain a neck clearance of .004-.005. Too much clearance can contribute to concentricity issue and most likely require sizing the necks in two steps. Starting at .0015 - .002 is a good range and let your rifle tell you what it likes. Lots of things can effect neck tension even when using the same die and bushing. For instance, running a neck brush prior to seating. The main thing is to have consistent neck tension. Best way to check neck tension is with a chamber seating die and a arbor press with a gauge such as the Century 21 Hydro Bullet Seater. Use one myself and sort rounds by neck tension for F Class.

 

[Whitshot]

Thanks for your responses, I’ll add a bit more information for you. I measure my fired brass at .295 so it’s spec. I have bushing dies here’s what I find

Neck turned then with loaded round is .286 outside diameter
My bushing die is .284, so tension is good,
Question is is .008 clearance to much? That’s what I hear is the main concern.

Will that much stretch greatly reduce my case life?

 

[spife7980]

Its not the end of the world. I certainly wouldn’t take anymore off than you have already. Go with where you’re at now. If the brass suffers prematurely so be it, can’t go back now. But I don’t think it’s trash immediately. Anneal it and you might never notice the difference.

 

[straightshooter1]

Thanks for your responses, I’ll add a bit more information for you. I measure my fired brass at .295 so it’s spec. I have bushing dies here’s what I find

Neck turned then with loaded round is .286 outside diameter
My bushing die is .284, so tension is good,
Question is is .008 clearance to much? That’s what I hear is the main concern.

Will that much stretch greatly reduce my case life?

I think this little piece should answer most of your questions: https://www.sinclairintl.com/guntech/neck-turning/detail.htm?lid=16038