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Brass neck thickness variation, does it show up on target?

Mulligan

Mulligan

Silver $$ Contributor
I have seen plenty of small groups shot with unturned brass. No doubt there is some variation in the neck thickness both in individual cases and the set of cases.

Does this variation show up on target?
If so, how much variation in neck thickness is acceptable?

Here is where I am coming from.
I have a both a .272" PPC reamer and Dasher reamer. Both require me to turn the brass due to thicker new brass necks.
So, I have to turn brass and my ability to do so is not yet perfected, nor is my ability to use a mic. In other words, I see variation in my measured turned necks. I am not sure how much of this variation is real or faulty mic handling or both? Even though I would like to say I know how to use my measuring tools and I have fairly good equipment, I assume some of the variation I am seeing is error from the same loose screw on the end of the stock that causes some flyers.

Thanks
CW
 
I use a 21st Century lathe to turn my necks. The turning mandrel and cutter is mounted in a rubber shock joint so that the mandrel can follow the alignment of the neck. If this were not possible, I can clearly see how neck thickness would vary when the neck is not perfectly aligned with the axis of the brass case. My guess is that your thickness variation has something to do with this.
 
Well, there's a lot of variables in shooting that make groups small or cause flyers. If you are a benchrest competitor, then the perfection of all those things become paramount. But if you're like me, like to reload and shoot small groups on paper, and want to hone my craft as a challenge, I'd guess that small variations in the thickness of the necks that are actually turned, would not be much of a factor, not necessarily worth buying a whole new expensive neck turner to solve.
Flyers for me are probably caused more from wind variations during my shooting, which I'm now going to start using wind flags to get a better handle on. Or might be the charge is just a little too hot, and that causes flyers. Could be lots of stuff, but probably not slight variations in a turned neck. I'm sure folks might not agree, just my .02 worth.
 
Mulligan said:
Good point, I should have stated I shoot BR and some f-class.
I turn with a PMA turner and generally see 2-3 10ths variation, but sometimes more.
CW
Click to expand...

Are you measuring the neck diameter with a bullet seated? (Using a micrometer)

I'm fairly new at this and have trouble measuring the neck thickness with a ball/tubing micrometer. When I measure the diameter across the neck on a loaded cartridge then it's more consistent. Especially after the brass has been fired a couple times.
 
Seems to me this question is directed at consistent bullet release regardless of bullet/brass mass or the sequence of neck expansion or bullet movement. When getting into neck thickness and irregularities I think you are approaching the gnat’s a** consideration of precision. Records have been set with both turned and unturned necks. If you turn, you are doing it because you are not sure how neck thickness variation affects your particular rifle and load. I definitely fall into the group who turn to the best of my ability just to make sure I’m not leaving something on the table. With that line of thought, 0.0002” variation is better than 0.001”. Can you see the difference on target? I think it depends on the shooter, the rifle, the over all quality of the reload, and the current conditions. If I tested the question and did see a difference, I’m not sure I would believe the result. And it sure wouldn’t be the only reason I continue to turn.
 
Well actually, I turn because I ordered a reamer to "my" specifications based on input from "pros" and my measurements........ AND then the new brass came our a bit sturdier! When I ordered a .272" neck, that was a no-turn, back in the good old days...... a couple of years ago.
So now for me, because I like some clearance and my rifle does also I turn.

CW
 
To answer he OP’s question, I thought I knew, but am beginning to have doubts.

I have always turndown necks. To me, it is just part of Benchrest.
However, back before the last Tackdriver, Bart stated he as shooting a .273 neck no neck turn PPC. He had just won the NBRSA 3-Gun.

So I borrowed a .273 neck reamer from Dusty and reamed one of my good barrels.

Then I discovered that the latest Lapua 220 Russian as a little thicker in the necks, averaging around .0145 with around .0005 variation in wall thickness.

the average loaded round measured right at .272.

Too tight.

But I tried it anyway and the darned thing shot great.

I have been turning my brass to .0118 to use in my .269 neck, which gives around .002 clearance for the loaded round With my own 68 grn FB.

Since I have at least 200 neck turned cases, I will shoot these for a while. But then I might order a .274 reamer.
 
jvw2008 said:
Seems to me this question is directed at consistent bullet release regardless of bullet/brass mass or the sequence of neck expansion or bullet movement. When getting into neck thickness and irregularities I think you are approaching the gnat’s a** consideration of precision. Records have been set with both turned and unturned necks. If you turn, you are doing it because you are not sure how neck thickness variation affects your particular rifle and load. I definitely fall into the group who turn to the best of my ability just to make sure I’m not leaving something on the table. With that line of thought, 0.0002” variation is better than 0.001”. Can you see the difference on target? I think it depends on the shooter, the rifle, the over all quality of the reload, and the current conditions. If I tested the question and did see a difference, I’m not sure I would believe the result. And it sure wouldn’t be the only reason I continue to turn.
Click to expand...
Just some things to ponder is all.
I remember a good discussion on this subject from a few years ago on BRC, involving an engineer or two. It made me look at it differently even if I didn't get any absolute answers. It still made me think. I've been shooting no turn necks for a few years now in short range BR and have had some good success. Not saying anyone should change what works but it's always good to question the status quo, IMHO.
It sure makes brass prep easier!

I do think .274- .2745 is the way to go for the new 220R Lapua brass. I prefer the old stuff but it it what it is.
 
Being a machinist, my proclivities won't let me put loads together that aren't concentric as I can make them. Even if I only skim .0005 to clean them up, that's fine. I just can't come to grips with having a chamber indicated to .0001 or better, and then knowingly put a case in it with the neck offset .0005. I also believe it makes a difference in accuracy.
 
Last edited:
butchlambert said:
.0002"-.0003" when a hair is around .005" That ain't much is it?
Click to expand...
I think the typical human hair measures between .0015-.0028” Butch. I’ve measured my girlfriend’s hair before at .0019” to explain to her “this is how much I’m looking to move the shoulders back”. Lol.
 
Last edited:
Bronsin said:
Being a machinist, my proclivities won't let me put loads together that aren't concentric as I can make them. Even if I only skim .0005 to clean them up, that's fine. I just can't come to grips with having a chamber indicated to .0001 or better, and then knowingly put a case in it with the neck offset .0005. I also believe it makes a difference in accuracy.
Click to expand...
I feel the same way. That’s why it bugs me so much that the no neck turns I tried shot so darned well.

It is contrary to everything I have been doing for years in short range Benchrest.
 
I turn necks for my .266 chamber in a 6br. I use PMA model A and B tools. I am able to get very consistent results, within .0002. The model B turns necks for .013 to .011, then model A goes from .011 to .009. Consistency comes from excellent equipment (using carbide cutters, a properly sized mandrel, good lube and an excellent case holder/ driver). Developing good technique is also key. It took me a couple sessions to get technique down.

On target, it ties into neck tension. Consistent neck tension is important for consistent accuracy.

PopCharlie
 
PopCharlie said:
I turn necks for my .266 chamber in a 6br. I use PMA model A and B tools. I am able to get very consistent results, within .0002. The model B turns necks for .013 to .011, then model A goes from .011 to .009. Consistency comes from excellent equipment (using carbide cutters, a properly sized mandrel, good lube and an excellent case holder/ driver). Developing good technique is also key. It took me a couple sessions to get technique down.

PopCharlie
Click to expand...
That is the same setup I use. My variation is bigger, but the majority are within .0002"...as I measure them.
CW
 
Mulligan said:
That is the same setup I use. My variation is bigger, but the majority are within .0002"...as I measure them.
CW
Click to expand...
BTW: I use 3-in-1 oil as a lube. This made a big difference by keeping heat down. Heat is the enemy while turning necks.

PopCharlie
 
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