Neck turning info question....

[griffgil1]

Hi all, new to forum.

Just getting started reloading for precision rifle (.308) and have a question regarding neck turning. Using the 21st Century turner and lathe setup and new Lapua brass. Having a hard time figuring out how much to remove. First problem is that I don't know how "out of round" is too much to begin with----- .001 .002 ???? When I measure the necks on the concentricity gauge they are all different, some having as much as .004 range on the dial. Next, when trying to improve concentricity by turning I keep taking off more and more material, but the best reading I can get is about .003 and I don't want to keep shaving them down too thin. I am sure that my problem is me and my lack of experience, knowledge, and understanding (and not the tools and equipment). Some enlightenment from more experienced folks would be greatly appreciated. Thanks, Griff

 

[22BRGUY]

Concentricity is not what you're looking for at this point...it is neck wall thickness. For that you will need a ball micrometer that can measure neck wall thickness to see how uniform it is before and after neck turning. Hope this helps.

 

[fdshuster]

Not all runout is caused by varying case neck wall thickness. You said "new Lapua brass", so it sounds like it's never been loaded and fired. Virtually all brass, no matter even the high quality Lapua will have runout in the brass as it comes out of the factory box. One or two firings will straighten out the case, so there will then be little, if any runout. Just to prove it: take a few of the worst (.004?), load & fire them, then check for runout again.

Depending on your chamber neck diameter, you may want to only clean up the slight differences in neck wall thickness. A quality tubing micrometer is a requirement, and to clean it up by outside neck turning, all you want to do is remove the high spots, so when you look at the turned neck there will be areas that were untouched by the cutter. Measuring with a tubing mic. would then show an even, consistant thickness around the circumference.

As an example: on my 6BR Lapua brass, out of the box, I will measure neck wall thickness of from .012" to slightly less than .013". After a cleanup cut, it will be a uniform .012".

 

[CatShooter]

Hi all, new to forum.

Just getting started reloading for precision rifle (.308) and have a question regarding neck turning. Using the 21st Century turner and lathe setup and new Lapua brass. Having a hard time figuring out how much to remove. First problem is that I don't know how "out of round" is too much to begin with----- .001 .002 ???? When I measure the necks on the concentricity gauge they are all different, some having as much as .004 range on the dial. Next, when trying to improve concentricity by turning I keep taking off more and more material, but the best reading I can get is about .003 and I don't want to keep shaving them down too thin. I am sure that my problem is me and my lack of experience, knowledge, and understanding (and not the tools and equipment). Some enlightenment from more experienced folks would be greatly appreciated. Thanks, Griff

As the others have said... don't turn them - shoot them 2 or 3 times. Then ask the questions, after you have measured the fired neck diameter and neck wall variances.

The 308 brass is outstanding right out of the box.

 

[spclark]

Neck turning serves two basic functions. First is to "uniform" neck thickness.

As others have suggested, doing this to raw, new unfired brass should be aporoached with caution. Using most turning equipment, you're not doing anything but making neck wall thickness consistent. Firing brass once or twice (in a properly concentric chamber & not in an M1 or M1A) will allow the brass to better conform to your rifle's chamber.

Second purpose is to tune the gap between a fired bullet just leaving the case neck and the chamber's neck diameter. Thinner brass will yield to pressure more rapidly, but if the chamber neck's significantly larger in diameter than your loaded ammo the brass gets worked more.

I just started using a 6.5 WSSM rifle. New Win 25 WSSM brass has necks ~ 0.019". Open them up to 6.5mm / .243" & not much changed. With a chamber neck of 0.304" I decided to turn new brass to 0.016" which is a lot! But the proof is great at 600 yards, it's super accurate! If I take another 0.001" off now I'll need to use a smaller neck bushing (0.293") next time. Using an 0.295" now & loaded ammo measures 0.297" at the neck for 0.001" neck tension.

For 308 I'll turn new Lapua brass to 0.013" at first, then down to 0.012" after a couple firings.

 

[BoydAllen]

Shoot them a few times, and while you are getting that done, pick up a ball mic. Don't be one of those "fellows" that think that he can get it done with the tips of his calipers. Have fun.

 

[griffgil1]

Thanks for all the replies! Now I am a bit more confused though. Everyone here replied that I should shoot the brass a couple times before measuring/turning, but most, if not all the reading I've done (including an article on the 6mmbr by Jacob Gottridson) indicate using virgin brass?? Isn't the idea to prepare the brass to the tightest specs and consistency before shooting it? Please don't get me wrong here, I'm not questioning all of your advice in any way- I'm just confused because I am getting conflicting information and don't know which is more accurate. I know there is a learning curve here (going from pistol and shotshell reloading to precision rifle), so I am trying to be patient when it's in my nature to try and figure everything out yesterday :-[ Thanks all.

 

[BoydAllen]

If you have a tight neck chamber, you have no choice, if not, you do. With a chamber that allows using unturned necks, it is not even clear that there is an advantage to be had by turning necks, (particularly given the quality of Lapua brass) assuming the best sizing practices are used. If you use the proper size of expander mandrel, that fits you turning mandrel, of course you can turn your unfired necks, but unless you pick up the proper tool to measure neck thickness to .0001, you will be working at a distinct disadvantage, hence the advice. You may now be giving up much, if anything, depending on the rifle and chamber design, shooting the unturned brass, this will let you start your tuning right now, and when you neck mic, arrives you can set about measuring necks, and deciding how think you want your necks. Tell us about your rifle, its chamber dimensions, and the manner that you load, or plan to load for it, including the equipment that you will be using.

 

[Phil3]

Griff,

It appears you are confusing two separate issues. Concentricity and neck wall thickness variation.

1) Concentricity measured at the neck indicates if the neck is centered with the case body.
2) Neck wall thickness variation indicates how much variation there is in the neck wall from one place on the neck to another.

When you use your concentricity gauge, you are seeing indicator movement because the neck is not concentric, or the neck wall thickness varies, or BOTH. You must address each separately. How to do this, and if others see my advice as incorrect, please say so!

1) Measure neck wall thickness using a ball type micrometer or the Redding gauge. I use the Redding and it is fine. This will tell you the thickness of the neck in each place you measure and the readings can be compared to see neck wall thickness variation. You may see .013" thickness in one place, .011" in another, .012" in yet another, etc. In this instance, the variation is .002", the difference between high (.013) and low (.011) readings.

2) Turn the necks to the degree you want. Some shave off enough to contact 70% of the brass on the neck, others turn enough so the entire neck is turned.

3) NOW, you can measure concentricity, as the neck walls are consistent in thickness, which means that any indicator movement on the concentricity gauge IS due to concentricity and NOT neck wall thickness variation.

4) If there is concentricity variation or runout on virgin brass (and my experience is, there will be, even on Lapua), shoot it. The pressure will blow out the case to a mirror image of the chamber, minus a bit of case springback. If the chamber is straight, you will find the case neck has very little runout if any.

If shooting in a production rifle, there may be little benefit to neck turning. Boyd gives great advice and his information to my past posts, and that from others, is what led me NOT to buy a neck turner for my SAAMI spec guns, especially with the Lapua brass I use in the bolt gun. Besides, the more you turn the neck, the more the neck has to stretch to fill the chamber, and that potentially shortens case life, though I have no evidence of that.

Just my $0.02, and hopefully worth that.

Phil

 

[griffgil1]

OK, I think I'm getting the picture. I understand now that I was confusing two different measurements as one in the same: neck wall thickness and concentricity. But....what I still don't get is this (and forgive my seemingly too-detailed questions, but I'm way too techno minded and like to understand the physics of this): if the purpose of turning the necks is to minimize neck wall thickness variations around the circumference of the neck, then what about the inside of the neck? It seems like there would still be variation in thickness, but it would be from the inside, as this has not been touched. A bad analogy would be to picture a doughnut with a perfectly circular and smooth outside circumference, but the inside surface of the doughnut hole is not circular or smooth- you would still read a lot of variation in "doughnut thickness", no matter how much of the outside you shaved off or how perfectly circular it is, because the inside surface is not even and circular.

As for my equipment, rifle, and purpose: I am interested in getting into medium and long range competition (F/TR specifically). Rifle is a Savage 12 F/TR. Reloading dies are Redding competition dies. Neck turning tool and expanding die are 21st Century. Case trimmer is Forester. Lapua brass and SMK 175 gr. pills.

Also, it seems like most experienced precision re-loaders know their chamber and chamber neck specs for their particular rifle, and I can certainly see why this is almost required information in order to do a proper job. Can I get this info from Savage? Or would they even have it, considering it is not a custom rifle?

 

[Steve Blair]

Also, it seems like most experienced precision re-loaders know their chamber and chamber neck specs for their particular rifle, and I can certainly see why this is almost required information in order to do a proper job. Can I get this info from Savage? Or would they even have it, considering it is not a custom rifle?

[br]
Have a gunsmith do a Cerrosafe chamber cast and then you will know what your chamber is, not what the factory might think it is.


http://www.brownells.com/gunsmith-tools-supplies/barrel-blanks-tools/barrel-chamfering-accessories/cerrosafe-chamber-casting-alloy-prod384.aspx

 

[BoydAllen]

First of all, there is a level of precision in brass prep. that is appropriate to your rifle that can be exceeded, but doing so will only cost you money and take your time, with no commensurate improvement at the target. This is not a criticism of your rifle or Savages.
When you turn your necks, you will first use a mandrel to expand them to properly fit your turning mandrel. Stretching them in this way tends to even out their interior shape, reducing the lumps and bumps. One this has been done, with proper lubrication, the turning tool is employed to make the thickness of the necks more uniform, proper attention to technique in this step should result in necks that vary by no more than +-.0001 and based on many years of experience by many shooters in parts of the shooting sports that achieve higher accuracy than is the norm in F Class, this is sufficient. In fact, as I mentioned earlier, if optimum tooling and procedure is followed you may not be able to tell any difference, at the target, between your unturned Lapua cases, and those that have been turned. What I am saying is that is not only a point of diminishing returns, but a point beyond which there are none. If you want something extra to do. look into annealing, and very precise weighing of powder charges. Both are proven reducers of ES.

As far as your chamber neck goes, a good rough estimate can be had by measuring necks of fired cases and adding .001. For your purposes this should be close enough. When using a bushing FL die to size brass that has expanded to a fired diameter that is typical with most factory chambers, there are some tricks that have been known to improve concentricity.

You might also take a look at using a Wilson trimmer. And avoid cleaning all of the powder fouling out of your case necks.

 

[22BRGUY]

If you go to Grafs.com on the web and type in GR22 it will show a pic of the type of ball mic you will need to measure the case neck wall thickness....best wishes

 

[M14AMU]

Read this:

http://riflemansjournal.blogspot.com/2009/12/reloading-neck-turning.html

 

[Steve Blair]

And avoid cleaning all of the powder fouling out of your case necks.

[br]
This is not necessary with larger bullets, Boyd. I clean my brass with stainless pins and anneal every firing. Here is a series of three five-shot groups 68.6-68.7-68.8 in a .300 WSM firing 230 Hybrids at the indicated velocities. The necks are very clean with just under .002" tension. [br]

Max Min Avg ES SD
2950.20 2939.70 2945.10 10.50 4.21
2948.70 2935.40 2941.00 13.30 5.76
2954.50 2941.10 2948.36 13.40 4.98

 

[BoydAllen]

I made a mistake?!!! Can't be. Tell me it's not so. ;-) Seriously...thanks for the info, and the data that gives it excellent credibility. I make no secret that I spend most of my time with smaller calibers, and the consensus at the highest levels of short range benchrest agrees with the apparently misplaced advice that I gave, for a different situation. (We don't see a lot of .308s in short range group shooting these days, and as you know ES is not nearly as important as at the longer ranges.) Again, thanks for the information. I will not forget it. Do you think that your approach to cleaning would be as successful if you were not annealing? In addition to making bullet pull more uniform, and ES smaller, do you think that it lowers bullet pull for a given amount of neck tension (difference in sized and loaded diameters)? Along that same line, are you turning necks, and if so, how thick are they? While we are at it, since your numbers are excellent, how much neck clearance are you using? As you can see, I am attempting to go to school on your experience.
Boyd

 

[mikecr]

griffgil1 you're thinking past the basics of neck turning. It's really a lot easier.
The whole inside-vs-outside variance in thickness is taken care of with neck expansion -to fit a turning mandrel. This drives variance outward to the cutter.
You don't turn new brass until reading low runout. You turn it for a set thickness, and then fireform to produce low runout cases from it.
The best time to turn necks is when it's NEW, unfired, right out of the box. You expand for mandrel fit and turn full neck length + ~30thou onto shoulders. Then fireform.

I agree with Boyd's advice on avoiding over cleaning of necks. There is no gain in it, and it increases seating forces(which is bad), same with over annealing.
Clean necks shoot the same as fouled necks, because 'pull force' has nothing to do with 'grip force'. But bullet/neck interface friction does increase seating forces, and this amplifies wedging with seater stems on ogive radius variances.

 

[Steve Blair]

I made a mistake?!!! Can't be. Tell me it's not so. ;-) Seriously...thanks for the info, and the data that gives it excellent credibility. I make no secret that I spend most of my time with smaller calibers, and the consensus at the highest levels of short range benchrest agrees with the apparently misplaced advice that I gave, for a different situation. (We don't see a lot of .308s in short range group shooting these days, and as you know ES is not nearly as important as at the longer ranges.) Again, thanks for the information. I will not forget it. Do you think that your approach to cleaning would be as successful if you were not annealing? In addition to making bullet pull more uniform, and ES smaller, do you think that it lowers bullet pull for a given amount of neck tension (difference in sized and loaded diameters)? Along that same line, are you turning necks, and if so, how thick are they? While we are at it, since your numbers are excellent, how much neck clearance are you using? As you can see, I am attempting to go to school on your experience.
Boyd

[br]
Well, I don't think you made a mistake. There's just more than one way to do it. The other point, that you already alluded, is that this is just one facet of what is required to produce low ES. [br]
Annealing is a big part of keeping neck tension consistent, for me. I have about ¼" of bullet engagement in the neck. The necks are turned to .0122" ±.0001". The die used provides ~.0018" neck tension at that thickness. It seats easily with a modified Wilson die but has enough grip to hold the bullet securely. My loaded neck is Ø.333", fired in a Ø.337" chamber.

 

[BoydAllen]

Steve,
Thanks for the rundown. I always enjoy learning from a good source such as yourself.
Boyd

 

[Centerfire]

You never mentioned if you are using an expansion mandrel matched to the neck turning mandrel as the first step in the process.
You are looking to keep your case length the same, the neck tension the same, eveything square, etc. Do you have a gizzy to check how far you are setting the shoulder back?
Since you have a Savage you can do the cerrosafe yourself. Directions included from Brownells.
By finding out the chamber size at the neck, first you can determine the minimum amount you need to remove to clean up your necks.
Does your sizing die have replaceable bushings?
By establishing the chamber dimensions first for this barrel you will then be able to determine the neck thickness and purchase the correct bushing.
If you purchase a tight neck replacement barrel in the future you will know what to do to get the correct bushing for that barrel.
Hope this helps
Centerfire