Bullet Runout

Barrelnut said:

I think your 550 yard steel group is missing in the post.

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Yup here's the 550 yard group. I get woke up two to three times a night caretaking. And I work so sometimes I'm a bit off in the mornings.

I don't shoot a lot of groups after I finish working up loads. I'll shoot to distance and then take them out hunting. Both of these are coldbore hits. The rock chuck was at 533 yards. The badger was 659 yards. Both with my budget build 260 AI. 145 gr Match Burners. So yeah making ammo with the least amount of runout is desirable. But it's not the end all be all.

Barrelnut said:

The Sinclair (like many others) measures runout from case neck to bullet tip.

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No, the Sinclair does not measure runout from necks to tips.
V-blocks measure full length total runout. They don't conceal anything.

The neck benders pin both ends and indicate very near one side. This, showing very little of actual total runout.
Think arc measure of a spinning jump rope. You would properly measure in the middle of arc, NOT at one pinned end.

Your ammo is not straight until it measures so on a v-block gauge.

I haven't seen much effect from a few .xxx runout. By the time it travels 26 inches of barrel, does run out have an affect? I don't think so.

Biggest cause of runout is excessive brass movement. Period.

I can measure my brass at ANY stage throughout the loading sequence and have less than .001" runout. I do not move my brass in ANY direction more than .003" total.
If you use .004" neck interference or more, you better have a really good seating system because all brass has a side that yields easier, even on turned brass, it's the way it's drawn. This causes runout.
Let me say this, I no longer measure for runout, it's irrelevant on groups anyway. The throat of your chamber WILL straighten things even though plenty say it doesn't. I shot groups with my normal loads and another group with .008" runout, the only difference was the shape, size was the same at 600.

Ever heard of chasing your tail?

Cheers.

xsn10s said:

I get woke up two to three times a night caretaking.

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Brother, you have the toughest job in the world. Be strong, and God bless!

Put my elk load together today for my 280AI - headed to Colorado for 3rd Season.
Using virgin Hornady brass, a Hornady Microjust seater with the proper seating stem inserted (I have 9 stems to choose from) I seated 60 rounds. Of those 60 I have bullet runout from .0005" - .003" as measured on my Sinclair. Better tools I suppose. I want that bullet traveling as straight as possible down the bore from the get go. This load - put together the same way time after time - shoots cloverleafs @ 100. I'm going to take advantage of everything I can - voodoo, prayer or luck.

What I have personally found about runout is it has a lot to do with brass hardness and bullet seating.I can start with new or once fired brass that starts out near zero runout and around three or four times the brass has been fired and resized,I'll start seeing more runout.I can anneal that same brass and the runout is reduced.If you have a bunch of cases that are a mixture of number of times fired,you will probably see your runout all over the place.The best thing I've found is to keep your brass segregated by the number of times fired.If you start seeing a lot of runout,anneal it.I think a lot of the runout tends to happen when seating the bullet in brass that has harden to the point it has too much neck tension.

baldhunter said:

What I have personally found about runout is it has a lot to do with brass hardness and bullet seating.I can start with new or once fired brass that starts out near zero runout and around three or four times the brass has been fired and resized,I'll start seeing more runout.I can anneal that same brass and the runout is reduced.If you have a bunch of cases that are a mixture of number of times fired,you will probably see your runout all over the place.The best thing I've found is to keep your brass segregated by the number of times fired.If you start seeing a lot of runout,anneal it.I think a lot of the runout tends to happen when seating the bullet in brass that has harden to the point it has too much neck tension.

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I plan to anneal this batch after they are fired. I did make a few changes yesterday on loading, I tested a case neck before sizing showing zero runout, then with FL sizer die with the decapper installed checked case after sizing and showed .004 runout. Next case I checked before sizing had zero runout, resized with same FL die without the decapper and came out with zero runout. So, the decapper rod is causing some of it, I have a Lee decapper die I used it to remove primer, then installed my 21 Century Mandrel and set neck tension, I checked my runout afterwards and still holding zero runout. I seated bullet and verified alignment and came away with .002 runout on some, zero runout on some and .004 on others. I was able to correct some of the bigger runout by reseating several times rotating half turn. I will pull out my annealer after I fire these rounds and anneal to see if things can be improved.

The root cause of runout is sizing of thickness variance.
So among the ways to address this, you can measure new brass thickness variance (at necks, which runs FL) and cull out offenders.
Where you don't do this, you leave yourself an abstract.

Mandrels.