Acceptable neck turning variation

[Kevin1990]

Just curious from the perspective of the benchrest and precision crowd. When you neck turn what is an acceptable variation between loaded rounds? I know we're shooting for .0001 and under, but is .0002 acceptable? If you had some pieces between .0003-.0005 would you just cull them and call it good?

I'm just curious on this, I mean it certainly has to matter i'd think as far as bullet release? Then again, I see guys shooting and winning with no turn necks. Also, wondering if some of that variation is just user error.

Thanks fellas

 

[gunsandgunsmithing]

Ime, factory Lapua is within about .0005 or so out of the box and neck thickness consistency has never been proven to be what I'd call a significant factor to br type accuracy. Opinions vary a lot but the results vary less when tested head to head.

 

[neckturner]

I know we're shooting for .0001 and under, but is .0002 acceptable?

If you turn with a decent tool and without rushing it, you'll see .0001 no problem. Also assumes your bullets are uniform.

 

[Kevin1990]

Ime, factory Lapua is within about .0005 or so out of the box and neck thickness consistency has never been proven to be what I'd call a significant factor to br type accuracy. Opinions vary a lot but the results vary less when tested head to head.

Thanks Mike! Reading some old threads on here from 2008 to 2010 people make it sound like you'd be better off culling the entire lot if you have more than .000001 variation lol. I just like to ask because I know opinions can change through experience and testing.


I just checked some loaded 6br with factory lapua and I am seeing .0003 out of the 20 I measured. Just measuring anything I can to try and get a better feel and confidence with this mic.

If you turn with a decent tool and without rushing it, you'll see .0001 no problem. Also assumes your bullets are uniform.

Probably so, but I've got some variation in mine. I was turning while the mandrel was hot and rushing a bit. Just wondering if that variation means anything on paper, pun intended.

 

[shoot4fun]

Heat is a big factor. Rushing the cut and heating up the brass and mandrel are detrimental to good results.
consistent execution of the process is another. I know people that can turn a thousand and keep the neck walls within the .0001 but I'm more in the .0002 camp.

 

[222Jim]

Just don't try to remove too much in a single pass. How much is too much? I get best results when I limit a single pass to removing less than 0.0015" and try for 0.0005" for the final pass.

Brass is funny.........if you try to remove too much in a single pass, it actually "piles up" like snow in front of a snow shovel. That makes achieving consistent results difficult. And keep the neck and arbor lubricated. Then getting less than 0.0002", which is tighter than many people can consistently measure, is achievable.

 

[mgunderson]

Ime, factory Lapua is within about .0005 or so out of the box and neck thickness consistency has never been proven to be what I'd call a significant factor to br type accuracy. Opinions vary a lot but the results vary less when tested head to head.

Some lots this is true Mike. Spent a good amount of time turning necks for br and 308 and that level of tolerance out of the box is crazy talk. Br is one of the more consistent, but i wouldn't say every br lots sre the same.

As a side note. I am a fan of the new cardboard boxes. The neck are super right out of the box.

 

[gunsandgunsmithing]

Some lots this is true Mike. Spent a good amount of time turning necks for br and 308 and that level of tolerance out of the box is crazy talk. Br is one of the more consistent, but i wouldn't say every br lots sre the same.

As a side note. I am a fan of the new cardboard boxes. The neck are super right out of the box.

Yeah, I probably should've made it clear the cases I was referring. They were predominantly 6.5 grendel, 6br and 220 Russian. Ill go a bit further and say that more recent brass isn't nearly as consistent from lot to lot but that within those lapua cartridges and over a few hundred lots, I stand by my post.

But further, I did follow up my prior post stating that this has just never been proven to be as much of an actual factor to accuracy as it is a perceived one.

I've checked this a ton, so its not a small sample. Its the very reason I've gone to no turn chambers on my br stuff.

I paid a reputable source to turn necks for me because I didn't have time. They ran within about the same .0005. I have always held tighter tolerances than that when I turn my own but the reality was, it didn't matter on my targets.

edit...I'm referring to total variation over a loaded round, fwiw. JMO but measuring neck wall thickness is the least accurate way to go about actually telling what matters and that's the diameter of what goes into the chamber. I use wall thickness to get me very close when setting up the neck turner but I rely on the loaded round and a good ol mic for KNOWING my chamber to cartridge clearance. Frankly, I'm not really sure where the whole idea of measuring wall thickness came from. It's both less accurate and you stack tolerances vs just keeping it very simple by just measuring over the neck with the bullet you're gonna shoot. It's easier, doesn't require special tools, it's more accurate and it's the only dimension that matters.

So, why do people refer to neck thickness so much? Why is that the standard people use so often? I really don't understand the logig, other than setting up the turner.

 

[DJSBRS]

Heat is a big factor. Rushing the cut and heating up the brass and mandrel are detrimental to good results.
consistent execution of the process is another. I know people that can turn a thousand and keep the neck walls within the .0001 but I'm more in the .0002 camp.

"consistent execution of the process is another".
That is the only process that will get you the same results.

DJ

 

[neckturner]

Just wondering if that variation means anything on paper, pun intended.

I don't think so, and certainly I can't shoot the difference.

Not aware of any formal, double-blind statistically valid test on this subject.

 

[Tod Hendricks]

If you’ve got the time and desire for consistency.

Run your expander mandrel through the neck, do your initial turn, then run the same mandrel back through again and take a second cut with the same cutter setup.

If you are generating heat, do 10 or 20 then go back and do the second cut.

Most consistent results I’ve found. Whether that matters is too subjective to answer, plus after a couple firings the brass will flow and show variations.

 

[DJSBRS]

Consistent cutting tool pressure, torque speed along proper lubrication is key to keeping precision variation tolerances.

DJ

 

[Kevin1990]

Thanks for all the responses everyone! I'll keep all this in mind when turning next time. It's not something I do often so it's hard to hone the skill, also perhaps not worth the headache as opposed to sending it out.

Also, I don't think my math was "mathing," or I didn't say it right.
I've been reading a bit more on old threads and a lot of people say +/- .0001 from the target measurement. How I'm interpreting that means a variance of .0002 all in all. If you shoot for let's say .3295 and have some at .3296 and some at .3294 you call if good? That how I'm reading it anyway.

95 percent of my brass is .3295-.3293 so I'm not gonna fret over it and just go shoot it. Hell, I can't shoot the difference anyway if there was one.

 

[DJSBRS]

Thanks for all the responses everyone! I'll keep all this in mind when turning next time. It's not something I do often so it's hard to hone the skill, also perhaps not worth the headache as opposed to sending it out.

Also, I don't think my math was "mathing," or I didn't say it right.
I've been reading a bit more on old threads and a lot of people say +/- .0001 from the target measurement. How I'm interpreting that means a variance of .0002 all in all. If you shoot for let's say .3295 and have some at .3296 and some at .3294 you call if good? That how I'm reading it anyway.

95 percent of my brass is .3295-.3293 so I'm not gonna fret over it and just go shoot it. Hell, I can't shoot the difference anyway if there was one.

Most reloaders can't hold the brass to consistently measure along with the ability or tools to measure consistently .0002 neck wall thickness.

DJ

 

[jimmymac]

Most reloaders can't hold the brass to consistently measure along with the ability or tools to measure consistently .0002 neck wall thickness.

DJ

^^^^^^^^
Hell yeah!

 

[jimmymac]

Just went through 100 pieces of Alpha Brass without issue. Consistent RPM’s and feed speed are the real deal. Don’t heat up your tool. Step away and come back to it. Spot check your work.

This is easy enough to do with quality tools and attention to detail.

 

[ELR LVR]

For true consistency in Neck Thickness
I like to expand and inside ream first
Size down then Outside turn next
---
I also take a second final cleanup pass on the OD, brass seems to allow for a second cleanup cut

 

[SKWERLZ]

Heat is a big factor. Rushing the cut and heating up the brass and mandrel are detrimental to good results.
consistent execution of the process is another. I know people that can turn a thousand and keep the neck walls within the .0001 but I'm more in the .0002 camp.

Heat and turning immediately after expanding.

I’m perfectly happy with a few tenths variation