Neck Runout Question

[Mule3006Elk]

When measuring runout do I measure total runout? Meaning, the sum of the positive and negative.

Example: If I have 0.002 and - 0.002 is my total runout 0.004?

I see some 1/2 this number and say it's only 0.002.

I'm not ocd with runout just trying to see which reloading steps are inflicting runout.

Just ran 28 pieces. 30-06 Lapua brass, Redding bushing die, SAC bushing, 21st Century Mandrel. Total runout (sum of + and -) of my case necks. I have not loaded them yet.

12 are 0.0015 or less
5 are 0.002 to 0.0025
8 are 0.003 to 0.0035
2 are 0.004 to 0.0045
1 is 0.006

 

[BBob]

Most common and proper used in reloading I would say is total runout. Yours is .004” aka .004” T.I.R. (Total Indicator Reading). It’s used to see how far off axis the object may be.

The half reading is Circular runout. It is generally used to see how round something might be not how far off axis it may be.

It’ll be interesting to see if TIR correlates at all between the bare brass and the brass once it’s loaded. I’m sure I did the same many many years ago but don’t remember the outcome.

 

[Mule3006Elk]

Most common and proper used in reloading I would say is total runout. Yours is .004” aka .004” T.I.R. (Total Indicator Reading). It’s used to see how far off axis the object may be.

The half reading is Circular runout. It is generally used to see how round something might be not how far off axis it may be.

It’ll be interesting to see if TIR correlates at all between the bare brass and the brass once it’s loaded. I’m sure I did the same many many years ago but don’t remember the outcome.

Thank you. Is there a threshold, say 0.004" or higher, remove from lot? In my example 25/28 have 0.0035 TIR or better. Is there any point of keeping 0.004 or higher in the mix?

These are hunting rounds, not BR, but I certainly enjoy seeing tight groups. My field shot max is 400 yards but I shoot in the off season out to 600-700 max.

I know this topic can be a rabbit hole. I understand this is not bullet TIR. Not sure if a case neck with poor TIR is worth keeping in the mix. Looking for general thoughts?

 

[BBob]

IMO I’ll bet you cannot shoot the difference with anything you’ve measured so far in a field rifle (and likely any sort of target rifle) and that will apply to the same runout in loaded ammunition. IMO .004” or so TIR will make no difference whatsoever in how your rifle shoots.

As I said I’d measure up seated bullets and see how it correlates to the bare brass to decide if it’s worth checking the bare brass. See if that .006” TIR still ends up with more runout than the rest of them. I bet it doesn’t correlate if using a good chamber type seating die like a Redding.

FWIW My runout gauge almost never sees the light of day anymore. There’s a lot of reasons for that. Things I learned from measuring as you are doing and figuring out what mattered and what didn’t. A lot goes into it. Part is what dies I use, part is the gunsmithing (chamber design), etc….

 

[JGRaider]

I'd be just as, or more concerned with runout after the bullet is seated. One reason I use LCD's as often as possible.

 

[Mule3006Elk]

I'd be just as, or more concerned with runout after the bullet is seated. One reason I use LCD's as often as possible.

LCD I am unfamiliar. I have Redding Bushing dies. I briefly read online about LCD. With my bushing dies I control the neck sizing. With LCD do they size to a universal standard? Just curious how they work. Thanks

 

[BBob]

LCD I am unfamiliar. I have Redding Bushing dies. I briefly read online about LCD. With my bushing dies I control the neck sizing. With LCD do they size to a universal standard? Just curious how they work. Thanks

The mandrel shipped with the die I would say is close to what a -.002" bushing would be. You can order undersized mandrels to reduce the neck size further. I have experimented with and use the LCD on a couple of cartridges. They can work well and I have no problem using them. They may need a little cleaning up and polishing of the die and collet. I do that to all of mine and I don't think I follow the factory use instructions.

 

[Mule3006Elk]

The mandrel shipped with the die I would say is close to what a -.002" bushing would be. You can order undersized mandrels to reduce the neck size further. I have experimented with and use the LCD on a couple of cartridges. They can work well and I have no problem using them. They may need a little cleaning up and polishing of the die and collet. I do that to all of mine and I don't think I follow the factory use instructions.

Great explanation. I couldn't find the 0.002" data. But in your experience sounds like I'm chasing my tail.

I might get better objective data by culling cases that shoot poorly and reverify if they should poorly. If so, keep those separate from the shooter cases. That sounds very interesting TBH.

 

[JGRaider]

You can have the best runout numbers known to mankind after neck/full sizing brass, but if your seating die doesn't seat 'em straight..........

 

[TaperPin]

Thank you. Is there a threshold, say 0.004" or higher, remove from lot? In my example 25/28 have 0.0035 TIR or better. Is there any point of keeping 0.004 or higher in the mix?

These are hunting rounds, not BR, but I certainly enjoy seeing tight groups. My field shot max is 400 yards but I shoot in the off season out to 600-700 max.

I know this topic can be a rabbit hole. I understand this is not bullet TIR. Not sure if a case neck with poor TIR is worth keeping in the mix. Looking for general thoughts?

You can always check how runout affects group size by writing the runout on each case with a sharpie and segregating them. Write down both neck runout and bullet runout to see how closely they are correlated.

It won’t make much difference, but each rifle is different, so you won’t know for sure until shooting them. It didn’t make even 1/16 MOA difference the last time I checked a load for bullet runout by shooting best vs worst in a very accurate rifle, but some people have seen more than 1/16 MOA. Personally, I don’t check runout unless the gun consistently shoots 1/2 MOA or less, but there’s nothing wrong with doing it all the time.

 

[BBob]

But in your experience sounds like I'm chasing my tail.

Imma dummy and can’t help from trying things for myself so I know what they actually do. No you won’t be ahead by using an LCD over a Redding bushing die so yeah IMO I’d agree that you’d be chasing your tail.

The LCD is good if you want to save $$$ but it will make you add steps to your reloading and it takes a little more finesse to use and you might have to work on it before it works properly.

As to culling cases and verifying I highly doubt you can verify that in a field rifle. But don’t let my opinion stop you from trying. It might work for you.