Why I measure concentricity on every load batch

[dstoenner]

I use a Redding Competition seater normally. Had read on here how everybody uses the Wilson chamber seater so I invested in a press and seater. I then took a batch of my neck turned fired 3 times Lapua brass and split the cases at random. The cases were rolling all 1 or 2 mil runout at the neck. I then loaded 20 with my Redding and 20 with the wilson. I then sorted on concentricity.

The end result was that 10 in each batch were .001 runout, then the Redding had 8 .002's and 2 .003 while the Wilson had 7 2's and 3 3's. Statistically equal.

Then there is the article where German Salazar did a comparison study of seating dies. #1 and #2 tied were Redding Competition seater and Wilson Chamber dies.

I have only had 2 times that I remember of having all of the loaded rounds roll only 1 or 2 mil runout. Nothing more and never all 1.

I am even now keeping records on each batch of Lapua brass on my 6X47L about the distribution of runout to see if I can detect any curves over number of times reloaded.

I am methodical.

David

 

[dsculley]

Mark your cases that have bad runout to see if they are the common denominator. I don't remember who the shooter was (probably some on here may), but there was a good shooter that, if he had an unexpected flier would cull that piece of brass to be used only for foulers.

 

[Mark W]

Mark your cases that have bad runout to see if they are the common denominator. I don't remember who the shooter was (probably some on here may), but there was a good shooter that, if he had an unexpected flier would cull that piece of brass to be used only for foulers.

I call that sorting by exception.

 

[dstoenner]

Mark your cases that have bad runout to see if they are the common denominator. I don't remember who the shooter was (probably some on here may), but there was a good shooter that, if he had an unexpected flier would cull that piece of brass to be used only for foulers.

In my match brass I haven't experienced a flyer that wasn't my fault. I did see that post where he said he ground it in by his boot heel. Now that is what I call serious.

In my last load batch of my 6x47L i had sorted out 74 for a match and the remaining 18 went in a companion box. I use those for my velocity check of the load and zero check of my scope. I do that the week before. This group of 18 were all .003 runout. I kept them separate and when the 74 were shot up I then loaded all 92 again. I loaded the 18 and measured concentricity. In the group of all .003, I had 5 that rolled .001, 2 that rolled .002 and 11 that were still .003. The 74 were about the same as the previous loading in runout with a couple of 3's out of the batch. Overall the density of 1's and 2's increased from the previous reloading cycle by about a net of 5 more.

Even the 3's are useful at 100 yards so I see no reason to scrap them. If I did have something really weird show up on one case, I would put it in my back pocket and take it home and measure the heck out of it to see what might be at issue. I don't want to kill the evidence

David

 

[VaniB]

Yep, when I'm target shooting and seeking tight bench groups I check each handloaded cartridge on my 2 Sinclair gages. I use one sinclair gage to check run-out of sized cases, and the other sinclair gage to check run-out on the completed cartridge. I then write the concentricity rating in black marker on the cartridges.(ie; .0035 thousandths of run-out is written as a "3 1/2" on the cartridge case, .002 is written as "2") I always shoot 5-shot groups and jot the ratings of the 5 cartridges onto the target next to each fired group. This way I know weeks or months later when I review my notes, that my cartridges were true and I can't blame a bad group on bad concentricity.

Any cartridge with over 5 thousandths does not compete and gets used as a "fouler round" or for sighting in a new scope. Checking run-out of each cartridge is as important to me as weighing the bullets, and annealing the cases for equal bullet pull.

 

[JFrank]

Mark your cases that have bad runout to see if they are the common denominator. I don't remember who the shooter was (probably some on here may), but there was a good shooter that, if he had an unexpected flier would cull that piece of brass to be used only for foulers.

I would be gettin low on brass quick using that system.

 

[JFrank]

Yep, when I'm target shooting and seeking tight bench groups I check each handloaded cartridge on my 2 Sinclair gages. I use one sinclair gage to check run-out of sized cases, and the other sinclair gage to check run-out on the completed cartridge. I then write the concentricity rating in black marker on the cartridges.(ie; .0035 thousandths of run-out is written as a "3 1/2" on the cartridge case, .002 is written as "2") I always shoot 5-shot groups and jot the ratings of the 5 cartridges onto the target next to each fired group. This way I know weeks or months later when I review my notes, that my cartridges were true and I can't blame a bad group on bad concentricity.

Any cartridge with over 5 thousandths does not compete and gets used as a "fouler round" or for sighting in a new scope. Checking run-out of each cartridge is as important to me as weighing the bullets, and annealing the cases for equal bullet pull.

Have you recorded any difference in point of impact from one case to another?
I cannot truly say runnout has effected any of mine. I’m curious as to your findings.
Appreciate your time
Jim

 

[Robert Weidler]

Why are you measuring in milliradians ?

Maybe you're trying to say millimeters ??? if so, then 1 millimeter equals to 0.039" inch. Which is HUGE runout.

Some think it suave/cool to mix measurement systems. There is no dimension "milli-inches" so if you mean thousandths say thousandths. If you mean millimeters say millimeters. Don't mix apples and oranges if you are not making a Ceasar Salad.

 

[dstoenner]

Some think it suave/cool to mix measurement systems. There is no dimension "milli-inches" so if you mean thousandths say thousandths. If you mean millimeters say millimeters. Don't mix apples and oranges if you are not making a Ceasar Salad.

I guess you didn’t see my Wikipedia update that shows mils to be a valid abbreviation of a thousandth of an inch.

The problem is that we live in a world of mixed measurement systems.

david

 

[dstoenner]

Yep, when I'm target shooting and seeking tight bench groups I check each handloaded cartridge on my 2 Sinclair gages. I use one sinclair gage to check run-out of sized cases, and the other sinclair gage to check run-out on the completed cartridge. I then write the concentricity rating in black marker on the cartridges.(ie; .0035 thousandths of run-out is written as a "3 1/2" on the cartridge case, .002 is written as "2") I always shoot 5-shot groups and jot the ratings of the 5 cartridges onto the target next to each fired group. This way I know weeks or months later when I review my notes, that my cartridges were true and I can't blame a bad group on bad concentricity.

Any cartridge with over 5 thousandths does not compete and gets used as a "fouler round" or for sighting in a new scope. Checking run-out of each cartridge is as important to me as weighing the bullets, and annealing the cases for equal bullet pull.

I sort of do the same. I sort each loaded round and put them in order in my ammo box. Then I record on a post-a-note what slots are 1,2,3 etc in the box. Then I shot in order. Like you the worst are used for foulers.

David

 

[Zero333]

Some think it suave/cool to mix measurement systems. There is no dimension "milli-inches" so if you mean thousandths say thousandths. If you mean millimeters say millimeters. Don't mix apples and oranges if you are not making a Ceasar Salad.

I agree, but at the same time most people say "Caliber" when they mean "Cartridge / Chambering".
When someone at the range asks me "what caliber are you shooting", I always answer "24" or "30" or 6mm etc... Then I continue to tell them "chambered for the 243winchester or 300winmag or whatever I'm actually shooting.

 

[VaniB]

Have you recorded any difference in point of impact from one case to another?
I cannot truly say runnout has effected any of mine. I’m curious as to your findings.
Appreciate your time
Jim

Yes, there is a difference between a .004 and a .008 cartridge. I have determined that there is absolutely no difference with .001" to .004" run-out readings of my cartridges when I desire the tightest 5 shot groups 1/4" MOA at 100 yards. But I still feel pretty sure that run-out is OK up to about .005" or .006" when I'm at the firing range and that's all I have left to shoot. One may ask me "Well then why do you even shoot anything other then .001" to .004" ammo? Well you see, when I handload 25 cartridges quietly for 3 hours at 10:00PM at night after I told the wife goodnight, sometimes that's the way the cookie crumbles at the reloading bench. Not all of the cartridges come off of my Rockchucker press and Redding Dies in that .001" to .004" preferred range that I'd like. Sometimes I end up with .005, .006", and .007" too, and so I accept them. But .007 is the cutoff point in my mind, with .008" or .009" being rejected to fouler shots or they get taken apart.

And it's not like a .007" might spoil the group and .008" is guaranteed to spoil the group, as I've had many of them cluster right into a tight 1/4" 5-shot group. But it's over a long period of testing different caliber cartridges over the years that I see a pattern take shape that .001 to .004" are the same in accuracy, with .005 to .006" normally just as good that I can tell. I can tell you for sure that I've see groups get spoiled when firing .009" or worse.... so I know to keep a good distance from that and not go beyond about .007" run-off. But, haven't you and I both had near perfect .001" run-out cartridges end up as flyer shots too? Nothing is etched in stone that if it's a .001" it is guaranteed to go into a 1/4" MOA group, or if it's .008" it's guaranteed to spoil a group. That's why I said above; "I see a pattern" .

 

[Bob3700]

[
David,

Why do some cases have a TIR of .001"-.003" while others go over .006". Sizing die? Seating die?

How about the case itself? You stated that you turn your necks so that they are straight. Did you ever look at the distribution of brass in the base of the case? Measuring the variation of the brass thickness just above the base of the case might be interesting to see. Does that variation continue to the neck of the case?

If you turned your necks to just clean them up, you probably noticed that the cutter trimmed brass off of one side of the neck and not the other. The neck thickness varied some. That brass distribution carries thru to the rest of the case down to the head. When the cartridge fired and pressure built up in the case, the thick side of the case moved less than the thin side. This causes the case to warp into a banana shape and causes runout. The sizing die won't straighten that case back out.

Just for fun, take your loaded rounds that exceed .006" and mark the high side of the bullet with a marker. When you shoot those rounds, put them in the chamber with the indexed mark at either 12 or 6 o'clock. See how those rounds group compared to your .001"-.003" TIR rounds.

Just some thoughts to ponder.

Bob

 

[VaniB]

I sort of do the same. I sort each loaded round and put them in order in my ammo box. Then I record on a post-a-note what slots are 1,2,3 etc in the box. Then I shot in order. Like you the worst are used for foulers.

David

I don't belong to a club. I go to the public range. You know that NOBODY else at the public range does that with their ammo like you and I do. And when I explain it to a curious onlooker, they have nothing to say.... but I know they are thinking, "Lord this guy is an anal nut! LOL.

It's only recently that I started to write the run-off number "2" or "2 1/2" etc, on the cartridge case. What was happening was that i would leave fired cases on the bench and have their marked slots in the box open. If I was preoccupied with something else, I might take a cartridge out of the marked slot without paying attention and I would then not know which slot it came from and what run-off rating it was. Writing the run-off number onto the cartridge with a sharpie eliminates the confusion. I keep a little wad of steel wool at my reloading bench and quickly wipe the sharpie writing off of the brass when I'm ready to remove it. It comes off instantly. Try that.

 

[dstoenner]

[
David,

Why do some cases have a TIR of .001"-.003" while others go over .006". Sizing die? Seating die?

How about the case itself? You stated that you turn your necks so that they are straight. Did you ever look at the distribution of brass in the base of the case? Measuring the variation of the brass thickness just above the base of the case might be interesting to see. Does that variation continue to the neck of the case?

If you turned your necks to just clean them up, you probably noticed that the cutter trimmed brass off of one side of the neck and not the other. The neck thickness varied some. That brass distribution carries thru to the rest of the case down to the head. When the cartridge fired and pressure built up in the case, the thick side of the case moved less than the thin side. This causes the case to warp into a banana shape and causes runout. The sizing die won't straighten that case back out.

Just for fun, take your loaded rounds that exceed .006" and mark the high side of the bullet with a marker. When you shoot those rounds, put them in the chamber with the indexed mark at either 12 or 6 o'clock. See how those rounds group compared to your .001"-.003" TIR rounds.

Just some thoughts to ponder.

Bob

Bob,

Good questions and observations. My experience on Lapua brass after 2 firings will load less than .005 runout. And that may be only 1 or 2 out of 100. The rest fall into the 1-3 category with a smattering of 4's.

One thing I found out a few years ago at an F-Class match is about seating the bullets. We all have heard (I think) to seat 1/2 way then bring the handle up and rotate 180 and finish seating. That will raise your 1 and 2 runout from 30% or so to maybe 50%. This guy told me to do it in 1/3's. Seat about 1/2 on your first stroke, turn the cartridge about 90 and finish seating, then turn another 90 and basically bounce the handle at full stroke twice. I thought the guy was smoking something but I tried it. It got me another 15% or so 1's and 2's. It works.

About finding the high side and marking it then loading it in the chamber appropriately. German Salazar actually did that experiment on a match 30-06 at I think 600 yards and compared it to non marked at random higher runout and sure enough his groups were better with the marked. Maybe that would be good to get the last few rounds but in the matches I shoot I have enough 1's and 2's to make the whole match.

Van,

I agree with you that 1 to 3 runout at 100 yards is virtually the same on target. I cannot statistically differentiate groups shoot with all 1's vs all 2's vs all 3's.

I did an experiment with some LC cases for my Match AR that turned out about 10 that had .007 runout for the batch. I took 10 more that had .003 runout and shoot 1 group of 3's and then a group of 5's and then repeated. The group of 3's were running about .5 while the group of 7's were running about .7. I do not know if that is a linear distribution between those end points but it convinced me to never blindly take ammo to a match. Only the best.

Also denatured alcohol or paint thinner will take a sharpie off in a swipe.

David

 

[dstoenner]

I agree, but at the same time most people say "Caliber" when they mean "Cartridge / Chambering".
When someone at the range asks me "what caliber are you shooting", I always answer "24" or "30" or 6mm etc... Then I continue to tell them "chambered for the 243winchester or 300winmag or whatever I'm actually shooting.

Agreed and some people interchange bullet the projectile with bullet the loaded round. I digress

David

 

[MislMan]

Just a thought for people writing 2 1/2 on brass, might be easier to just write 1.5, 2.5, etc

 

[Robert Weidler]

I guess you didn’t see my Wikipedia update that shows mils to be a valid abbreviation of a thousandth of an inch.

The problem is that we live in a world of mixed measurement systems.

david

Fair enough, David. So, the next time you have a rifle built tell your gunsmith you want a one mil headspace.

 

[Dusty Stevens]

Fair enough, David. So, the next time you have a rifle built tell your gunsmith you want a one mil headspace.

if hes been around industrial environments he will know what he means

 

[dstoenner]

if hes been around industrial environments he will know what he means

Thank you