Definition of bullet runout

[Uncle Ed]

Really? You do this?
Have you engraved measured thickness variance onto each case(or some other system), so that you can do this subtraction on measuring runout off them necks?
I must be misunderstanding you.

Seems easier to measure loaded runout off bullet bearing, removing said thickness variance from reading.
You are right about the neck benders though(like the Hornady). They do not show much of actual runout.

If the neck runout reading is more than the neck thickness variation on a unturned necks, chances are you are inducing neck runout during sizing. My cases are again checked after loading and bullet seating for "bullet" runout.

If not checked this way you do not know if the sizing die is causing the problem or the seating die. If you just check the bullet runout after the cartridge is loaded you have no idea where the runout is coming from and are left scratching your head.

 

[mikecr]

On that Sinclair you can quickly move indication from necks to shoulders to unseated portion of necks to exposed bullet bearing, and see exactly where runout is originating on the case. No funny math, or funny stories about it, needed.

 

[Uncle Ed]

On that Sinclair you can quickly move indication from necks to shoulders to unseated portion of necks to exposed bullet bearing, and see exactly where runout is originating on the case. No funny math, or funny stories about it, needed.

To each his own, I want to know how straight my necks are "before" I seat the bullet.

If you do it your way you will need the Hornady gauge to bend the case necks to reduce the amount of runout.

And again this is on cases that are not neck turned, but even on neck turned brass I check neck and bullet runout.

And the best part about reloading is the person pulling the press handle decides how to do it.

 

[Lucky Shooter]

I agree with Uncle Ed on finding the source of runout.

I've checked many fired cases on the Sinclair gage and have never found
any appreciable runout on the outside of the fired cases-----have done this
so many times that I almost take this as a given----but Murphy still lives.

If the necks have been turned, logic says that the inside of the necks should
also run true. I've never tried to measure the runout on the internal surface
of the necks but think it might be interesting.

I think, usually, any runout has to occur in the resizing or bullet seating step.

My goal is to find the source of runout and eliminate it. Seems to be little benefit
in always checking runout after getting good case prep down pat.

A. Weldy

 

[Straightshooter1]

If the necks have been turned, logic says that the inside of the necks should
also run true. I've never tried to measure the runout on the internal surface
of the necks but think it might be interesting.

That's what I've found to be true . . . with not issue until the non-trimmed part (usually referred to the doughnut) works its way up to where it comes into contact with the bearing surface.

I think, usually, any runout has to occur in the resizing or bullet seating step.

In my experience . . . absolutely.

There are so many things involved, that make it difficult to identify just which are the cause(s).

For example: I was having a run out problem and I figure was mostly due to the seating die, so I sent it to the manufacturer along with some fired brass and bullets that I load. They sent it back with the inside of the die nicely polished. That did help, but still didn't reduce the run out to what they said I should be getting. Not long afterwords, I tried something I hadn't done in a long time by seating some loads to the COAL SAAMI spec of 2.800" (for my .308). Typically I seat out to at or near the lands to like 2.880. When I seated to the COAL of 2.800 I consistently got a run out of .001 or less. When I seated long, I'd often get run out from .002 - .003. So, the only solution I can think of for that is getting a custom die. (BTW, I also stopped using the expander ball, which is one of the things that helped a lot)

One thing for sure . . . listening to very experienced reloaders really had really helped me, keeping me from having to reinvent the wheel (so to speak). That one of the things I love about this forum and other's like it.

 

[mikecr]

The root cause of our runout is thickness variance. This, running full length of cases (it does).
Barring any direct problems with our reloading process, the action initiating runout is sizing cycles. More sizing, more often, of thickness variance, equals more runout.
Contributors to runout are case design, chamber specs, tool & die issues, misunderstandings of runout, and lack of upfront planning to prevent it.

If you planned to remove practically all runout, you would do the following:
- Choose a modern cartridge design
- Cull cases with thickness variance as measured at necks.
- Carefully measure about ~500 new cases for all dimensions & fill out your reamer print for no more than 1thou over the mean of each dimension bell curve. For this, plan on turning to set 1/2thou total neck clearance.
- Never size the brass (anywhere).
- Seat with an inline die, ~1/16" with first bump, turn case 180deg, finish full seating in one smooth move.

A bit extreme I suppose, but if loading for a 'low TIR ammo trophy' this is what you would do to get it.
For many other folks, it's very easy to see what you're doing to cause runout, or to keep it minimum for the cartridge design.
You fully fire form your cases with partial neck sizing only. Good time to measure & match H20 capacities, but it's also the straightest your brass will ever be. Should be under 1thou TIR as measured off mid necks. Partial NS no more than 2thou under cal, and use a mandrel for preseating/expansion. Runout at mid necks will go up here by ~3/4 thickness variance of necks (but bullets will seat straighter). You should still be in the 1thou TIR range. Now body size including shoulder bump, all minimal amount (always). See what you're TIR jumps to. Should be 2thou or less still. Seat bullets, measure runout just in front of mouths, on bullet bearing. Should be no more than 2thou.

Custom sizing dies greatly help here (even custom true FL dies)(but I would never, ever, FL size necks).
If your reloading something like a 30-06, or 270, etc., you'll be sizing more, and runout will be higher and grow faster. Might as well plan for bananas there and set sloppy clearances to avoid chambered tension points. There is no reason to fight it & I'm sure most 30-06 reloaders pay no mind to it.

 

[Lucky Shooter]

Thanks for the full process mikecr.

I'm not likeiy to go for the straight round trophy----just want my bullets
to be concentric with the bore when the round gets chambered.

There have been a few comments posted that I'd never considered. Live and learn.

I have no experience with "straightening" loaded rounds, don't know if this is a
good step but its not something I'd want to do.

Thanks to this thread, I should be able to do a better job.

A. Weldy