Reading a sinclair concentricity gauge
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redleg1013
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Not to get all GD&T, but let's not get roundness (circularity) convoluted with concentricity and runout.
If there is case wall variation, forget it, unless you map out the inconsistencies and then verify with an indicator, you're going to go mad chasing your tail looking for concentricity... tighten up on the circularity of the neck. Indicate along the case, if the case is banana shaped, you're going to again chase your tail since you won't know uf the case is causing the runout or the neck or both (at least not without devoting a fair bit of time per case). To put things simply runout = circularity + concentricity. You have to have one of them controlled, and let's face it, it is a LOT easier to control circularity. Use quality dies in a rigid O-frame (or multi-axial) press to minimize induced runout due to flex when sizing brass, then turn your necks (good news is you only have to do it once) to a uniform dimension (knocking off the high spots is second best) using the most reasonably rigid setup you can muster.
But at the end of the day it is up to the end user. If, like me, OCD demands and time allows go for it. I FL size without the expander (tool deflection is a real thing) in my Forster CoAx press, then expand on a mandrel, neck turn on a lathe (Forster original case trimmer).
If there is case wall variation, forget it, unless you map out the inconsistencies and then verify with an indicator, you're going to go mad chasing your tail looking for concentricity... tighten up on the circularity of the neck. Indicate along the case, if the case is banana shaped, you're going to again chase your tail since you won't know uf the case is causing the runout or the neck or both (at least not without devoting a fair bit of time per case). To put things simply runout = circularity + concentricity. You have to have one of them controlled, and let's face it, it is a LOT easier to control circularity. Use quality dies in a rigid O-frame (or multi-axial) press to minimize induced runout due to flex when sizing brass, then turn your necks (good news is you only have to do it once) to a uniform dimension (knocking off the high spots is second best) using the most reasonably rigid setup you can muster.
But at the end of the day it is up to the end user. If, like me, OCD demands and time allows go for it. I FL size without the expander (tool deflection is a real thing) in my Forster CoAx press, then expand on a mandrel, neck turn on a lathe (Forster original case trimmer).
GW Hunter
Well-Known Member
I appreciate everyone's input. Thanks. I ordered a Sinclair last night. I'm anxious to see what I've been producing using a type s bushing die and Forster ultra seater. Haven't gotten in to neck thickness yet. That's my next toy...
Mikecr
Well-Known Member
You can learn a lot watching brass change through reloading stages and then reloading cycles. Loaded ammo w/new brass will have really bad runout. This doesn't matter.
Same cases Fully fire-formed with no body sizing, necks turned and/or mandrel expanded, will provide for loaded ammo with least runout. Then there is everything in between.
The root cause of our runout is thickness variance in cases. This can simply be measured at a mid-neck datum, and assumed to run full length of cases (it does). In itself this hurts nothing as it's hammered inside cases with fire-forming. But we add a dominate contributing factor toward runout -with sizing.
Sizing provides the evil energy this witch is hungry for.
The greater the area sized, esp. length, and the greater the yielding by sizing, and the higher the frequency of sizing, the harder & faser runout grows.
Given this, you may eventually consider reduction of these sizing attributes.
Once in a while a die, or press, or chamber causes problems, but this is more rare than implied at forums.
If runout eventually bothers you so much, you could eliminate it all together with an upfront plan. It's entirely possible. I got an excessive thing about making straight ammo myself, but I also know that reasonably crooked ammo can still shoot well. Just don't allow the runout to exceed chamber clearances, where it would cause chambered tensions, and contribute to flyers (like any random tension, anywhere else on your gun).
Same cases Fully fire-formed with no body sizing, necks turned and/or mandrel expanded, will provide for loaded ammo with least runout. Then there is everything in between.
The root cause of our runout is thickness variance in cases. This can simply be measured at a mid-neck datum, and assumed to run full length of cases (it does). In itself this hurts nothing as it's hammered inside cases with fire-forming. But we add a dominate contributing factor toward runout -with sizing.
Sizing provides the evil energy this witch is hungry for.
The greater the area sized, esp. length, and the greater the yielding by sizing, and the higher the frequency of sizing, the harder & faser runout grows.
Given this, you may eventually consider reduction of these sizing attributes.
Once in a while a die, or press, or chamber causes problems, but this is more rare than implied at forums.
If runout eventually bothers you so much, you could eliminate it all together with an upfront plan. It's entirely possible. I got an excessive thing about making straight ammo myself, but I also know that reasonably crooked ammo can still shoot well. Just don't allow the runout to exceed chamber clearances, where it would cause chambered tensions, and contribute to flyers (like any random tension, anywhere else on your gun).
J E Custom
Well-Known Member
Bullet Concentricity Basics — What You Need to Know
http://bulletin.accurateshooter.com/2019/02/bullet-concentricity-basics-what-you-need-to-know/
Thanks Bigedp51 Good article !!!
Everything to do with accuracy starts with the center line of the bore. The bolt, the action, the chamber, even the barrel thickness at any given point must be concentric to the bore if top accuracy is the goal.
A good smith knows of the importance of concentricity and a good re loader must know and understand it also.
If everything is done correctly the rest is up to the shooters ability.
Just my opinion
J E CUSTOM
Mikecr
Well-Known Member
Eccentricity/Concentric has always been an area of misunderstanding by reloaders, competitors, and manufacturers. For example; Sinclair merchandises their v-block runout gauge as a concentricity gauge. It isn't, and cannot indicate eccentricty.
There is a vast difference between a concentric item (anything centered) and a straight item. You can center a banana, but it'll always show high runout. Consider all the things we center in a lathe.
On the other hand, a straight item will always measure as concentric.
Often I get the feeling those embracing 'concentricity' have difficulty in making straight ammo. Their 'neck benders' as I refer to them, barely show 1/3 of actual TIR.
Truly it is not straight ammo, and chambering straight and stress free, until it is measured so on a v-block type runout gauge.
There is a vast difference between a concentric item (anything centered) and a straight item. You can center a banana, but it'll always show high runout. Consider all the things we center in a lathe.
On the other hand, a straight item will always measure as concentric.
Often I get the feeling those embracing 'concentricity' have difficulty in making straight ammo. Their 'neck benders' as I refer to them, barely show 1/3 of actual TIR.
Truly it is not straight ammo, and chambering straight and stress free, until it is measured so on a v-block type runout gauge.
bigedp51
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And if I read mikecr's posts correctly he neck sizes his cases.
Do you neck size your cases for your AR15 rifles.
I also like facts and expert comments.............and belong to the loaded round should fit in the chamber," like a rat turd in a violin case."
Kevin Thomas
Lapua USA
"There's two very common misconceptions that you've expressed here, and I'd like to address them both. One , that N/S extends the life of the brass. As I said, if done properly, F/L sizing gives you every bit as long of case life as N/S can, but without all the additional headaches that go hand in hand with neck sizing. You will have problems if you stick to neck sizing. It's not a question of if but of when. I tend to believe in Murphy in these things, and he'll usually find you when you can least afford a visit from him. And Two, that full length sizing somehow produces less accurate ammo than neck sizing. It doesn't, and is generally the other way around. Virtually all accuracy labs that I'm aware of use nothing but full length sizing for all their testing, and accuracy is what most reloader's dream of. I've fired literally hundreds of thousands of ten shot groups, with well over 95% of them staying far below the 1/2 MOA mark. In fact, when a rifle wouldn't consistently hold 1/2 MOA or under, I scrapped the barrel, as I could no longer use it for test purposes. All of that ammo was full length sized, NEVER neck sized, as it had to work in a variety of different guns. MY predecessor at Sierra, Jim Hull, used to say that a loaded round should fit in a chamber," like a rat turd in a violin case." Jim had a way with words, and creating visual images. But the idea is that it should fit freely, without binding or jamming when chambered. Forget the nonsense about N/S ammo giving better accuracy, because it's exactlyvariety that, nonsense. A few isolated examples of individual guns or groups don't change that, and it's the long run averages that count."variety
Germán A. Salazar
The Rifleman's Journal
"a full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway.
In conclusion, I believe that allowing the bullet to find a relatively stress-free alignment in the throat by full length sizing (including the neck) and turning necks to enhance concentricity gives the bullet the best probability of a well-aligned start into the rifling."
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J E Custom
Well-Known Member
Getting back to the OP question, What you are looking for is "NO" reading. There is nothing we can do about the inside of the case body And even though it is just a container that holds powder keeping the volume consistent will help. The outside of the case body is another thing all to gather. It should fit as good as possible and chamber with slight contact.
The reason for this fit, In spite of what some think is for accuracy. If the case is a good fit, and concentric, it will chamber the same every time regardless where the head stamp is clocked and remain centered in the chamber.
If the outside case body is concentric to the bore, and the neck is concentric to the bore, the bullet will be concentric to the bore if neck thickness is the same and in gauge the lands uniformly. If you over size the case simply seating the bullet against the rifling will only center the the ojive of the bullet and the rest of the bullet will be off center line and launch with some degree of yaw.
No question that full length sizing makes chambering easier, but it can reduce the accuracy potential, and over work the barrels rifling and the brass case it's self. To parallel this thinking, you would not want a motor or a pump shaft to have run out or be eccentric just like high performance engines have to have everything in perfect alignment and concentric to the bore where the part goes for the best performance.
I have never said that having perfectly concentric loaded ammo was easy, Just that it was Better. If accuracy is what you seek, then perfectly concentric ammo that fits the chamber perfectly should be your goal. How you achieve that and with what tools you use is your choice.
This debate will never be agreed upon and that's OK. It is just like the term used for computers "Trash in, Trash out" Quality takes effort and the outcome is rewarded with Effort. Nothing good is ever easy.
Just My opinion and belief
J E CUSTOM
The reason for this fit, In spite of what some think is for accuracy. If the case is a good fit, and concentric, it will chamber the same every time regardless where the head stamp is clocked and remain centered in the chamber.
If the outside case body is concentric to the bore, and the neck is concentric to the bore, the bullet will be concentric to the bore if neck thickness is the same and in gauge the lands uniformly. If you over size the case simply seating the bullet against the rifling will only center the the ojive of the bullet and the rest of the bullet will be off center line and launch with some degree of yaw.
No question that full length sizing makes chambering easier, but it can reduce the accuracy potential, and over work the barrels rifling and the brass case it's self. To parallel this thinking, you would not want a motor or a pump shaft to have run out or be eccentric just like high performance engines have to have everything in perfect alignment and concentric to the bore where the part goes for the best performance.
I have never said that having perfectly concentric loaded ammo was easy, Just that it was Better. If accuracy is what you seek, then perfectly concentric ammo that fits the chamber perfectly should be your goal. How you achieve that and with what tools you use is your choice.
This debate will never be agreed upon and that's OK. It is just like the term used for computers "Trash in, Trash out" Quality takes effort and the outcome is rewarded with Effort. Nothing good is ever easy.
Just My opinion and belief
J E CUSTOM
misterc01
Well-Known Member
Great info here! To your original question - no. It is the total value. When you rotate the case, the needle moves. Set zero on the gauge at the lowest point. rotate the case. The gauge will move and note the highest value. That is your total runout. If moves .002 then the runout is.002.
Mikecr
Well-Known Member
Well, pretty much anyone reloading is neck sizing, regardless of sizing die type.
An exception is with those running FITTED chambers for improved cartridges, allowing for no sizing (not even for necks).
Where you're running sloppy chambers and cartridges with poor reloading designs, You will have to size more. You made that choice with that path.
But this in itself does not broadly mean anything w/resp to better or worse results.
So it's possible somebody out there, somehow, is shooting ~1/4moa with an AR15. That's incredible and part of what makes all this so fun.
Mikecr
Well-Known Member
Yes, that's correct.
No lying, no cheating, and when it's straighter it won't move so much.
bigedp51
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- Joined
- Dec 10, 2010
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Once you get a neck thickness gauge you will ask yourself if you should start neck turning. And in a SAAMI factory chamber neck turning can mean the neck will expand more and sizing will work the brass more. So buying quality brass will reduce you prep time with your cases.
I have a RCBS ball micrometer and a Redding neck thickness gauge pictured below that I prefer to use. With the Redding gauge and one twist of the wrist you will see how much neck thickness variations you have. And if you do not neck turn you will need to subtract the thickness variation from the case neck runout reading. You can also use the Redding neck thickness gauge to sort your cases and not neck turn. I have had Remington .223 cases with .009 neck thickness variations, meaning this gauge will tell you a great deal about the quality of your cases. Normally the thicker side of the neck will run all the way to the base of the case.
J E Custom
Well-Known Member
To me a perfect fit is just that and doesn't have any measurable clearance. (Machinist call this a slip fit) because it will still chamber/move, but has no slack/clearance.
With proper sizing, and good dies that match your chamber, the case should fit like the chamber reamer did. In many cases the case has a slight crush fit so it cant move during firing. The only movement that can take place is neck expansion and a slight lengthening of the case due to pressure. The better the fit (Restraint), the less the case will lengthen.
J E CUSTOM
