Average runout?

[esheato]

What started as a quick check on die setup turned into an informal runout inspection over 72 rounds of 243 AI.

This is probably the best I can make ammo at this point in time.

Dies are Redding Type S neck bushing dies with the micrometer adjustment on top. Don't remember the bushing size, but it's correct according to Sinclair Intl for Lapua brass when I asked about it.

Load specs are fireformed Lapua brass with a Lapua Scenar 90 grain bullet.

I measured the runout on a Sinclair concentricity gauge. The tip of the gauge was about a third down from the tip of the bullet. The spread is as follows:

.000" 7 cartridges
.001" 21 cartridges
.002" 28 cartridges
.003" 12 cartridges
.004" 3 cartridges
.005" 1 cartridges

Not sure where that .005" came from.

I don't think that's half bad, what could be done to improve? Rotating the case halfway through seating?

Is this close to your averages?

 

[dakotasin]

yes, you are very close to what mine run.

i tried rotating the case partway thru, but that actually made mine a little worse. mine are at their straightest if i start off w/ them straight, and continue to refine them. make sure case mouths are straight (trimmed) before the first firing. after that, check neck run-out after sizing, reject the bad ones. just get the bullet started when seating, lower the ram to release pressure on the bullet, then finish seating.

that little stutter step seems to sometimes help, sometimes not, but at least it doesn't hurt. rotating the cases partway thru sometimes helped mine, sometimes hurt, so i quit.

i'll also add that not many guns or shooters will notice .004". i know you have some dedicated precision guns, and for those your groups will likely notice the .004", and probably notice the .003's. all your .002's and smaller shouldn't make a difference, and until you get the range backed off a bit it isn't real likely the 3's or even 4's will be a problem.

there are other little things you can attempt - like making sure the die and ram are under pressure when screwing your die in, or modifying your shellholder or ram where the shellholder goes - but this business of chasing run-out can really bring out the ocd in a person, and for the most part isn't worth the hassle. i'm aware of mine, i try to minimize it, but don't drive myself nuts over it, even for my 1000 yard guns.

i will also add that rams on presses are not always straight - there could be some run out on a ram. anyway... don't drive yourself bonkers - your numbers are on par w/ most.

 

[Dave P]

Those look like good numbers to me. I don't think you could improve them and see the difference on the target.

 

[ranger335v]

"The tip of the gauge was about a third down from the tip of the bullet."

That sorta means your runout reading is about one third less than your actual runout.

"The spread is as follows:"

Your spread is reasonably typical before neck turning and case selection to cull the obviously bad necks.

"Not sure where that .005" came from."

Cull that case. Maybe the .004"s too. No seater or sizer can correct for bad necks, we have to do that by selection.

" Rotating the case halfway through seating?"

A popular and oft repeated web self delusion. It presumes the die's seating stem is tightly fitted to the bullet guide chamber and that's rarely - if ever - true.

The rest of this 'essay' is aimed at the world in general:

Low runout is good. IME, a bullet that starts crooked will normally continue to seat crooked, and from the same direction, no matter how I may spin it around. You can confirm it with your own concentricity gage. Seat halfway (or what ever), remove it, gage and mark the high point, rotate half way and complete your seating, recheck. Bet you find the offset is still going the same direction and is only "decreased" by the leveraged amount the additional seating accounts for.

Many reloaders seem to want "high bullet tension", 3 or 4 thou is often mentioned, but that's also self delusion and does increase runout. Excessive "neck tension", ie, a neck ID (Inside Diameter) smaller than about 1-2 thou under bullet diameter simply requires a lot of excess pressure to seat but adds nothing to real bullet grip. Check that for yourself too, mike the diameter of a loaded round, pull the bullet and mike the same point on the neck, it will typically be a thou or a little less because that's all the springback the alloy can permit before it expands passed its elastic limit. Thus, all a smaller neck ID does is increase seating effort and that excess seating/neck expanding pressure almost invariably makes bullets cock to one side or another as they enter the bullet guide chamber of the die. Once they starts crooked, they usually stays crooked!

Solution: Get a size die/expander that only makes the necks small enough to hold the bullets securely (and remember that's really only about 1 thou, anything smaller than 2 thou under bullet diameter is too small) so no excess seating pressure will be required. Bushing type neck dies can do it but I love Lee Collet neck sizers for straight necks without fooling with any finnicky to use bushings. And I just use a common FL or Body die on the few occasions I need to set the shoulders back. A Lyman "M" expander OR Lee's long expander design used with an FL die is much better than using any conventional ball expander.

Neck turning can help reduce runout. Turning for factory chambers can easily be overdone and will only make a sloppy fit even sloppier. However, skim turning necks over maybe 60-70% of their circumference can improve even good necks and give a little lower runout even if the neck "tension" is too high. It doesn't require a BR grade neck turner to do this, my Forster HOT-100 hand held turner is moderately priced, works fine, has a very nice carbide cutter and a calibrated adjustment knob. I chuck my case heads in a battery powered VSR (Variable Speed Reversable) 1/2" drill motor and turn the necks at slow speed; no sweat, no pain, quickly done, never need to do it again and it certainly reduces my average runout.

 

[esheato]

that little stutter step seems to sometimes help

I've done that before and noted the same results.

i'll also add that not many guns or shooters will notice .004"

I realize this and I don't expect to see the results in my guns...especially when this stuff is 100 yard test ammo. Making the best ammo possible goes a long way to getting my head straight and eliminating possible excuses after the groups are shot.

but this business of chasing run-out can really bring out the ocd in a person, and for the most part isn't worth the hassle.

I completely agree. I've much better things to do than chase the little numbers around.

That sorta means your runout reading is about one third less than your actual runout

Care to elaborate on where I'm supposed to measure it from?



This is what I'm using.

Ed

 

[Ol` Joe]

Without neck turning I doubt you`ll get better numbers, what you are seeing now is likely the variation in neck thickness between cases.
If the rifle has a factory chamber I would more then happy with what you are building for it.

 

[ranger335v]

'..what you are seeing now is likely the variation in neck thickness between cases."

IF you're using the gage as it's shown in the photo, Joe is correct, you're only measureing any out of roundness in the necks.

Support the case at the shoulder and put the point of the dial indicator as near the point of the bullet as possible to check runout.