Neck turning - How much is too much?

[Wile E Coyote]

When one turns a case neck, what would the "minimum" allowable thickness be?

I have a box of 50, once fired brass that has neck wall thickness' between .010" at the thinnest and .014" at the thickest in each case. (measured with a Redding Case Gauge) The whole lot is fairly similar. If I turn these necks to something like .0105" to .011, will the neck wall be too thin to be safe? If this is acceptable, how thin could one turn the neck and not have a problem right off the bat?

The rifle chamber is SAMMI standard. It's not a custom chamber.

Thanks

 

[Darrel Martin]

First ,welcome to the forum. I think that even if you turned them all down to .010 there would not likely be an issue with safety, but I doubt you will gain much in accuracy as the chamber will likely have a lot of clearance .It may also cause the necks to split sooner as there will be a lot of expansion with firing and then contraction with resizing.
That being said,I certainly see where I would be unhappy with the brass if each case has .004 variation in thickness .The idea of skimming off a couple thousandths from the thick sides seems reasonable.I have brass turned to .010 in a couple guns,but they are tight necked match chambers in which this is required in order to get adequate clearance.

 

[Bulseyetom]

I agree with the last post. It seems like for a standard chamber most people turn just enough to clean up maybe 50% of the neck. I often thought that turning the necks so they are clean and then just neck sizing with a Wilson die which only sizes part of the neck might allow the part of the neck closest to the shoulder to center the case in the chamber but have never played with that beyond thinking. My Benchrest rifle required I turn to .082 thickness and they lasted 20 firings but the necks fit the chamber with minimum clearance unlike a factory chamber where you will have maximum clearance if you turn them too much. Just my 2 cents. Tom

 

[fdshuster]

As the above posts suggest, you will gain nothing by outside neck turning, for a SAAMI spec chamber. All you're doing is introducing an even greater amount of "slop" between the loaded case neck walls and the chamber walls.

If you're getting as much as .004" difference in thickness around the neck circumference, I would advise you get some quality brass. That kind of variance is unacceptable for anything but basic hunting accuracy. Forget about any type of accuracy requirements. Lapua if it's available for your rifle.

We are outside neck turning for tight, fitted necks where the loaded round neck diameter may ( for example) measure .267" for a chamber neck diameter of .269".

 

[jlow]

There seems to be some misunderstanding of the purpose of neck turning. Certainly neck turning is necessary for a match chamber so that the round would fit, but neck turning is also important for consistent neck tension so that you have consistent MV which is important for long distance precision shooting. This second reason is good for both rifles that have SAMMI and match chambers.

 

[Wile E Coyote]

Thanks everyone, I've been doin' some homework since I posted and have come to the same conclusion that this brass is almost junk because it is so out of shape.

I'm going to re-assign this stuff to my AR for plinkin and the like. In the meantime, some .223 Lapua brass has been ordered and should be here next week.

FYI - the last post before this mentioned "release" this concept is what I had in mind when I thought of turning necks. I just failed to say it well if at all. my apologies for being confusing if I was.

Thanks again for taking the time to answer.

 

[necchi]

you will gain nothing by outside neck turning, for a SAAMI spec chamber.

I wouldn't go that far.

Your certainly not going to cause undue harm making out of round brass necks closer to round.

 

[jlow]

Yes, more consistent neck thickness = more consistent “release” characteristics = more consistent MV = better precision!

I don’t think the brass you mentioned is junk – at least as you describe it. I use new LC09 brass and it can have the range of variation you mention and this brass is normally regarded as good brass by most. Certainly Lapua brass is better, but it will come in likely thicker but I am not sure with significantly less variance – have not used it but that is my understanding. You have not gone wrong by buying Lapua but I would keep the old brass and see what you find with the Lapua before you make your final conclusion.

 

[Wile E Coyote]

Thanks for the replys, I'm not scrapping the brass as in throwing it away. The most out of round stuff I'll load some plinkin' rounds for my AR. The few that are concentric are set aside for the future. And I'll take a few, turn and load them to just see how long it takes to split or otherwise damage them; moderate loads of course. Also to see if truing the necks, either partially or completely, makes any significant difference in ES and SD.
Thanks again

 

[Link]

Are all reloads for the AR?

thanks Link

 

[4xforfun]

My first true Match rifle and long range hunting gun were 300 wby's with a .330 neck. Loaded rounds came in at .328.....which gave me a neck wall thickness of .010. .308 + .010 + .010 = .328.

No problems.