Home Forums Reloading Big Game Rifles Bullet run out question

A few months ago, I had many questions about neck wall thicknesses and concentricity gauges. Mathman, as well as others, took time to answer my questions and steer me in the right direction. I bought a gauge and started paying closer attention to my reloads. I culled out brass that had neck wall thicknesses difference greater than 4 thous. and cartridge run out.

I even went so far as to buy a new Forster bench rest seating die. Imagine my surprise when my bullet run out was 9 thousandth. Any ideas as to what is causing that.

Thanks

What was the run out on your case necks before you seated?
are your case mouths good and square with a very nice smooth chammer?
Do your bullets feel like they're entering the case mouths with about the same pressure it takes to continue to seat them or does it take it quite a bit of push and they kind pop down into the neck?

Kraky
The run out on the case necks were 4 thousandth or less. The cases were trimmed and deburred before loading.
I'm gonna say the bullets enter the case smoothly or at least not with extra pressure, if I remember correctly.

Run out can happen for many reasons.

Press alignment / lack of play to self align is one of them. Have you floated the die base, and lock ring ?

I moved to a co-ax press, and it did improve my run out..

Are you getting 4 thousandths runout on the necks of fired cases?

If your chamber neck is round that shouldn't be happening IME.

I'm confused by the way you stated this. If you're checking neck wall thickness the cull number should be .001" or .0015" at the most.

How are you checking the neck wall uniformity?

If your sized brass has .004" runout on the necks then there is a brass problem (bad neck walls), a die problem, or both. I hate to see even .002" runout on the necks of my sized brass.

Sorry for the confusion I created. My fault for not doing a better job of using the correct terms. I am doing all my measurements on a RCBS casemaster.

I am getting neck wall thickness readings from .001 to .002 and neck wall run out readings up to .004 on sized brass. Brass with greater than .004 I culled. I assumed those readings were acceptable. When I seated a bullet, my bullet run out readings jumped up to as high as .009.

Maybe I was better off when I was ignorant of how far off these measurements were.

Here's where the diagnostics come in as I described in another thread.

Start with some cases that have .001" or less neck wall variation. This way you'll know the brass isn't the problem.

For fired brass it's best to take measurements with them deprimed. I recommend a Lee universal deprime die, they're cheap and work well.

Size a few pieces without the expander ball in place. Measure the neck runout. If it's more than a tiny bit then there's a die problem.

Now I'll assume the die checked out OK. So size some brass with the expander ball in place. Check the neck runout. If everything is good here then .002" runout would be the most I'd accept as OK, and would really prefer less. If there's a problem here it could be the expander assembly needs tweaking so as to not bend the brass on the way out. Or it could be the die is sizing the neck portion of the brass more than necessary and even a straight expander assembly has too much work to do and can't keep things straight. Some neck diameter measurements of brass sized with and brass sized without the expander will fill you in here.

A technique that can result in straighter sized brass is to deprime first in the universal die, size in the regular die without the expander, and then reinstall the expander assembly and push the case neck over the expander ball without going far enough into the die to size.

Now I'll assume straight sized brass is in hand. If the seater won't seat any manner of bullets pretty straight then there's a die problem. If the seater seats some bullet types straight and not others, then there's a compatibility issue with the seater stem and the bullets it doesn't like.

You could also try a different shell holder as a test. The one you're using may be machined crooked.

Very good explanation of the procedures, Mathman. Sizing with the expander removed then expanding by pushing the ball instead of pulling has solved most of my runout problems also.

With age comes wisdom.

What's the wisdom for dealing with those pesky unexplained flyers?

In my case, realizing that they have a great deal to do with me and very little to do with anything else.

If it doesn't make a difference for you then don't worry about it. Less hassle.

I get a lot of satisfaction out of improving my handloads, and I can see the difference on target which adds to the fun.

Whether or not it matters for me in the field when it's windy and the tree stand is swaying is a different question.

I agree with you on all points - especially the idea of keeping it fun. (If I could see on-target results of my attempts at improvement of my loads, I would pursue it further. As I said, my skill seems to make that point moot.) Best, John

Mathman and others, thank you for your contributions to my continuing education on reloading. The way you broke it down into steps was very helpful.

I admit the brass I am using is pretty worn. They probably have been reloaded at least five times. I will probably buy new brass and start from there.

what do you call acceptable as far as bullet run out is concerned?

Thanks

And new fancy tools that measure stuff to thousands of an inch or smaller can drive a loony.........loony......



Casey

I don't know how others think about runout, but I try for .003" or less on every thing I load for hunting. Varmint ammo (prairie dogs, groundhogs even less.