Home Forums Reloading Big Game Rifles Case neck thickness

For those that measure case necks for neck thickness uniformity, what is your dividing line between good-to-go and cull? This is for factory grade hunting rifles, not custom made or benchrest rifles.

The RCBS CaseMaster instructions say anything over 0.002" should be addressed/culled. But it seems as if I've read others (perhaps including J.B.) using 0.001" as their max tolerance.

What do you think?

I'd dump anything .002" or more, or use them for fouler rounds, rough sighters for newly installed scopes or the like.

I like to keep it down to .001" or maybe a dial indicator needle width more. With good brass it's easier to assemble straight cartridges, and I've found that to be more important than super precise weighing of powder charges.

I don't necessarily dump any cases, but I do sort them. I use ~0.001 as a max. I say ~0.001 because I like to sort in groups of 20 or 50 or whatever, and if I'm at 19 and there's a case that shows 0.0015 runout I'll probably keep it in the group.

The cases that don't make the cut are destined for practice rounds. The irony in these cases is they often outshoot the cases that have better concentricity, but they get shot a bunch and they get loaded with tried and true practice loads and inexpensive match bullets. Sierra Matchkings with 0.003 to 0.004 concentricity error shoot better than Partitions with perfect or near perfect concentricity.

But I wouldn't go shooting an elk with a Matchking. And I wouldn't waste money shooting Partitions at paper all year long.

I appreciate the feedback.

How much difference do you see on factory hunting rifles between 0.001" and 0.002"? Between 0.002" and 0.003"? And what kind of distance do you have to shoot before you notice a real difference?

I ask because from my preliminary testing last week there was probably 50% of the cases that were near, at, or above 0.002". Granted, I only tested about 20 cases but that doesn't bode well for the cull rate.

What kind of runout are you seeing for assembled cartridges in that batch of brass?

The brass with greater than 0.002" of neck thickness variation was culled. I only ended up loading 12 rounds as that was all that was needed at the time.

I didn't keep notes, but this is how I remember the concentricity readings.

2 rounds were between 0.000" and 0.001"
3 or so rounds were around 0.002"
5 or so rounds were around 0.003"
2 rounds were near or at 0.004"

Those figures aren't too bad. What kind of dies are you using?

I like to think there is nothing the brass makers do that I can't improve upon and with few exceptions I am seldom disappointed.

My opinion has it that other than case length I won't measure anything until after the first firing. Then I measure neck wall thickness. What happens next depends a lot on application and the exhibited tolerance window of the gun. Ultimately there are two issues at play. One is neck tension and the other concentricity. Being as lazy at the next oaf I will not twiddle with things that don't need it. Neck turning is an option sometimes, not always a requirement.

Mathman and Joel,

Are you guys talking about neck wall thickness or runout?

Setting aside neck concentricity for a moment, how much variation in neck wall thickness do you guys tolerate?

Casey

+1. Neck walls seem to get 'ironed' a bit after being loaded and shot, and the cull rate is lessened. I use .0015" as the dividing line. Only thing I do before loading the first time is primer pocket uniforming and flash hole reaming.

At the start I was talking about thickness variation, and I prefer no more than .0015", and I like .001" or less better.

Later I asked about the TIR on the bullet ogive to see how the OP's finished cartridges were turning out.

Unless one really has garbage, neck wall thickness issues can be easily rectified with a little turning/reaming. I use a RCBS tool that simultaneously reams and turns and work them after an initial firing. There's no springing away from cutters and very little variation when the wall is pinched between inside and outside.

As mentioned above, doesn't neck wall thickness not only affect loaded run-out but potentially neck tension issues upon ignition? Or are these variations small enough that if loaded run-out is good, then there is no need to worry about it?

These are standard RCBS FL dies, with the sizing die backed out enough that's its only partial sizing.

The other night I loaded a dozen rounds for the STW.

I'd turned the necks, and on all 12 the runout was under .001 each.

Same as Mathman, neck walls thickness. I sort with a Redding gauge for that purpose.

I also measure TIR of loaded rounds, and I normally cull (sighters or whatever) at 0.003. But I loaded 40 rounds this year for an elk hunt to get 27 rounds that had 0.001 or less runout. Then I only needed 1. Completely unnecessary as I shot a bull at about 75 yards.

I use either a Lee Collet Neck die or a Redding Comp Neck bushing die and a Redding body die to size, and either a Redding Comp seating die, Forster Comp seating die, or Wilson die for seating. I almost never see runout more than 0.003.

Necks wall thickness significantly affects total runout. In my estimation you can add the neck wall thickness variance and add die error (mostly sizing error, but potentially seating error with the dies I use) and end up with TIR.

I sometimes turn necks also, after sorting for neck thickness variance. Turning necks or using cases with neck thickness variance <0.001 has the potential to make loaded rounds with near perfect concentricity.

I agree with others that note neck turning may or may not be beneficial. And neck turning a bad case still leaves you with a bad case that just happens to have good neck thickness variance.

I honestly don't think I want to get into neck turning. I think I'll just cull anything over 0.0015" neck thickness and use the Tru-Angle tool to correct any ammo with run-out over 0.003".

I'd like as much hunting accuracy as my loads, firearms, and I am capable of, but would like to keep it reasonable. Neck turning just seems a step too far for my tastes and purposes.

I do appreciate all the feedback.

Azar, I'm late to this fire, so forgive a late response after so many have already answered, but I have one thing to add.

You said in the beginning you are are using the RCBS Case Master. I use the same gauge, and I have to admit I love it to find overall runout, but for checking neck thickness I think it leaves a bit to be desired. Sometimes I'll get pretty consistent readings, but at other times not so much. I generally load some tension on the dial readout and this helps, but it can still be inconsistent. I think this is because the case isn't supported anywhere, and even double/triple checking it makes me second guess it by its overall inconsistencies.

To combat this I've been using dial calipers and I've had much more consistent findings. I check in about 8 spots around the neck and cull as you mentioned if I have more than a .0015" difference.

Also, as mentioned above with neck turning. If the case wall thickness is off, it's most likely off all the way to the base of the case, so even if the neck is then corrected by turning, the rest of the case isn't necessarily concentric "internally."

I don't measure necks. fire forming usually irons out minor differences. If you're concerned about the neck being too thick and causing pressure problems, then a simple check is to slide a bullet into the neck of a fired case. If it slides in kinda easily, then you're good to go.
And finally, the proof of the pie is in the eating. What kind of groups are you getting?

I know this is contrary.....

I find a pretty low correlation between variation in neck wall thickness and neck runout. Same with neck thickness and bullet runout. I'm sure there will be a variation in neck tension on the bullet, but for the most part I'm talking hunting rifles.

But even my varmint weight Shilen doesn't seem to mind variation in neck wall thickness.

I have a lot of 243 WW brass that I measured for variation in neck thickness, but never sorted. About 40 pieces have neck runout of less than .001, all of them are less than .0025.

And yes, I have a Mitutoyo indicator on my fav concentricity gauge that reads to .0001 (that's not a typo).

The end game is straight ammo, if you can get there without turning or sorting brass necks, it makes life a lot easier.

Casey