OAL length discovery and how you all deal with it

[mikecr]

When you TEST for best seating(no assumptions), you'll likely come across something that puts a grin on ya face.
You'll see a node in it that falls within a window, outside of which the grin goes away.

Your window might actually be ~20thou, or 10thou, or it could be +/- 3thou. In the lands or off the lands.
Not a problem. It's very easy to set seating right where you want it.
And with this, I personally move on to meaningful ladder testing.

As to why seating is significant, I don't know for sure. I 'think' seating shapes our tuning window through pressure peak timing.
But I've seen over & over with hunting capacity cartridges that seating can hold the single largest affect to grouping. No amount of powder change can mess up grouping like seating adjustments can.
Smaller cartridges, like a tiny 6PPC or 30br, benefit from a tuning node established at a more extreme pressure peak. Seating for these is commonly taken into the lands. But even here, there is tuning(or group shaping) potential with seating adjustments that are relatively small.
No problem.

Don't blow off seating!

 

[Tuckerp229]

Tuckerp,
I've read this whole thing and I can recognize your struggle.
Your mixing two variables, bearing surface and OAL,.

I may be mixing more than one variable, but I have identified them and asked for advice to isolate them. Also, I thought I was clear that I am using the Hornady bullet comparator which measures length from the ogive to the bullet tail end.

Your right, bullets have different length, but your measuring device will actually measure from the same place on the ogive, (the datum, or more precisely, your datum point) just like your seating stem wil contact the bullet ogive at the same point while seating.

But this is my problem, if the ogive diameter varies as per Hornady, +/- 1 thousandths, and this variance is on a "slope", (which magnifies the error a bunch), one is not measuring the ogive on the same place bullet to bullet unless the two bullet happen to have the same size ogive.
My concern is that when I set my dies up to s specific length, lock the die down, recheck length and then start seating the remaining bullets into the cases, the ogive-to-tail end length varies up to 6 thousandths!

While your caliper tool and or seating stem may contact the bullet at different datums, it doesn't matter, your wanting to achieve only one goal, having the bullet seated to the same OAL as it relates to the ogive position of the bullet in the case,,,
AKA: Cartridge Over All Length
I bought the Hornady bullet comparator to change from the inherently inaccurate OAL to the suposedly more accurate goive to bullet tail end measuring.

The only way to get both exactly the same is to pre-measure all bullets in the lot and select only the same prior too seating.
As pointed out there are a whole mess of variables that mess with the rifle and shooter.
This is beginning to look like the only way but I am still dubious about where the length variable is sourced, 1. ogive circumference,2. bearing surface length, 3. boattail length-if any, and 4. squareness of the tail end of the bullet.

Bullet variables are just part of the game, here's a tip;
Take your calipers and gently close the jaws and adjust zero. Now open the caliper too read .006 on the indicator and lock it down,,
Hold the caliper jaws up to a light and look at the gap.
8) You've got alot of different thing to worry about than that little gap ;D 8)

You are correct, and I repeat all this is probably about details beyond my shooting abilities-none the less I was simply trying to establish "best reloading practices" since as as mikecr put it, "it is no more work to do something correctly than to do it incorrectly."(except of course trying to establish the which and how of these practices is proving difficult). My hope was to eliminate as many of the variables created at the reloading bench so as to have the range results be more about my shooting techniques.

Cheers,

And thank you for your time and help.

 

[Tuckerp229]

When you TEST for best seating(no assumptions), you'll likely come across something that puts a grin on ya face.
You'll see a node in it that falls within a window, outside of which the grin goes away.

Your window might actually be ~20thou, or 10thou, or it could be +/- 3thou. In the lands or off the lands.
Not a problem. It's very easy to set seating right where you want it.
And with this, I personally move on to meaningful ladder testing.

This is exactly what is proving to be not easy, hence I put the question out there for help from those of you who have gone before me. True, I can measure and set the seating die to the exact length I wish...but the following bullets can and do vary will the seating die is demonstrably locked in the original position.

As to why seating is significant, I don't know for sure. I 'think' seating shapes our tuning window through pressure peak timing.
But I've seen over & over with hunting capacity cartridges that seating can hold the single largest affect to grouping. No amount of powder change can mess up grouping like seating adjustments can.
Smaller cartridges, like a tiny 6PPC or 30br, benefit from a tuning node established at a more extreme pressure peak. Seating for these is commonly taken into the lands. But even here, there is tuning(or group shaping) potential with seating adjustments that are relatively small.
No problem.

This seems to speak to what Peter from Lee Precision said..." seating near the lands is about creating more uniform pressures within the case before the bullet leaves the case."

Don't blow off seating!

No sir, I ain't.
I'm just a trying to get it right

 

[mikecr]

Well I'll try to help a little.
My tools:
- Sinclair 'nut' bullet comparator: http://www.sinclairintl.com/.aspx/pid=34262/Product/Sinclair-Hex-Style-Bullet-Comparators
It's simple, free floating, and I use it for all logged values. It's just one of those tools that happens to work.
- Wilson micrometer top inline seating dies, with an arbor press: http://www.sinclairintl.com/.aspx/pid=39884/Product/Wilson-Sinclair-Hand-Die-Kit-w-Micro-Top
This is actually a less expensive system w/resp to quality threaded seating dies.
Again simple, free floating, precise adjustment, & positive stopping.
- Caliper: http://www.sinclairintl.com/.aspx/pid=41332/Product/Starrett-6-Electronic-Caliper
A less expensive caliper to .0005 works fine for this.
- As far as qualifying ogive radius, I use Bob Green comparators: http://greensrifles.com/New_Products.html
I also use a purpose built taper mic w/software to determine actual ogive radius(for BC calcs). But Bob's comparator provides a quick check of many bullets.

I also use wilson bushing neck dies(some custom), and Sinclair expander mandrels, to produce ~1thou of neck tension with semi-cleaned(carbon remaining) unlubed necks. I do not anneal until it's actually needed. With this, I have low seating forces that do not create wedging of the seater plug against noses.

For seating with a threaded press extra factors can muddle things up a bit. Mostly play in the press. I would use a micrometer type die & bottom the die to the shellholder for seating & may or may not cam-over. Depends on results.
Like mentioned there are many threads here to improve seating with this.

 

[necchi]

I think I wasn't clear in my previous post, I was actually trying to be helpfull.

if the ogive diameter varies as per Hornady, +/- 1 thousandths, and this variance is on a "slope", (which magnifies the error a bunch), one is not measuring the ogive on the same place bullet to bullet unless the two bullet happen to have the same size ogive.

For it's application too,, the position of the real bullet ogive as it applies to the bullets position in your rifle chamber, your tool is measureing the ogive at the same datum point on each bullet.



My concern is that when I set my dies up to s specific length, lock the die down, recheck length and then start seating the remaining bullets into the cases, the ogive-to-tail end length varies up to 6 thousandths!

Exactly, the variance of the individual bullets is now lost in inside the neck and body of the cartridge, as it applies to OAL your bullets are indeed seated to the same OAL . This is the topic here right? OAL?
When I seat bullets, (like you with common components,, for factory rifles) and measure for my select OAL after seating, I do see a variation also.
I have enough flex in my press that I can,, If the bullet is long, re-insert the bullet in the holder and press the lever harder to push that bullet in a little deeper, now I'm talking .002-.003 here.
It's really an operator finesse issue at the press, for me it's more than just yanking the handle up an down.
If a bullet is more than that far off It's put aside to have the seater plug adjusted after the bulk of the bullets are seated. There are other issues affecting that one case, perhaps case neck thickness or inside diameter or work hardening or spring back,,,,?

If Bullet body length variations of .006 is too much to be acceptable, Hornady bullets aren't the ones you need to use. I'm a Nosler fan,, and while they may indeed have the same kind of variable dispersion, I've found through experiance that my box of bullets fired tend to be more reliably accurate than the Hornady even with those variations.

I remember well when I began loading stressing over where that needle landed on my dial caliper, I've always been after the best ammunition I can make and do things right the first time too, but in this case .006 of body length with a Hornady bullet isn't a real factor for me.

The single most improvement I made in my technique was correcting runout issues at the press.
Using tools the "straighten" already bent ammo doesn't make sence to me. Haveing case necks and bullets come out of the press with reliable concentricity is an advantage that far exceeds minor bullet body variations.

 

[mikecr]

For it's application too,, the position of the real bullet ogive as it applies to the bullets position in your rifle chamber, your tool is measureing the ogive at the same datum point on each bullet.

Datums are 1st qualified by angles affecting them & without this taken to standard, reloaders often measure more or less variance than actually exists.
What Tuckerp229 is considering is that his datum isn't qualified from bullet to bullet. If nothing else, there is disparity between leade angle and varying ogive angles. With this, even while all OgvOALs measure the same with our tools, ogive radius variance can still change distance of or to contact with the lands.
And also(a side note), even while we're satisfied (via Buhay tool) that our bearing lengths match in a lot, if the datums were not qualified, the measure is probably invalid. The same holds with nose trimming(aka meplat uniforming). Until the angles are qualified this only serves to cause meplat diameter variance.

the ogive-to-tail end length varies up to 6 thousandths!
I hope by this OP means OgvOAL to casehead, and NOT to bullet base.
If it is to bullet base then this thread falls apart so far,, and yes 6thou of variance as combined boat tail, bearing, with unqualified datums(ogive radius/boat tail angle) is utterly meaningless.

 

[300 RUM]

Tuckerp229 you have so far been given bad information all the way around.
They represent appalling generalizations of reality.

-For one, it is very possible to seat bullets to EXACTLY the same OgvOAL.
It's just that bullets used to do this must be qualified in ogive radius and seating forces must be rational.
-Also, it is very possible to measure ammo at EXACTLY the same OgvOAL.
Again with qualified ogive radius(your datum), and consistent use of adequate tools.
-To end up with same relative seating distance your headspace needs to be set exactly, and again this is entirely possible.
-OgvOAL(seating depths) can be VERY important to accuracy, and should not be blown off by anyone.

I agree, my head spaces are +/-.0005 and same for bullet seating. if your bullets measure differently from one to another and they will depending on the manufacture, hornday states .007" on their tip to ogive record the lot number and call the manufacture to verify to be with in specs.

 

[BlackEagle]

When you TEST for best seating(no assumptions), you'll likely come across something that puts a grin on ya face.
You'll see a node in it that falls within a window, outside of which the grin goes away.

Your window might actually be ~20thou, or 10thou, or it could be +/- 3thou. In the lands or off the lands.
Not a problem. It's very easy to set seating right where you want it.
And with this, I personally move on to meaningful ladder testing.

As to why seating is significant, I don't know for sure. I 'think' seating shapes our tuning window through pressure peak timing.
But I've seen over & over with hunting capacity cartridges that seating can hold the single largest affect to grouping. No amount of powder change can mess up grouping like seating adjustments can.
Smaller cartridges, like a tiny 6PPC or 30br, benefit from a tuning node established at a more extreme pressure peak. Seating for these is commonly taken into the lands. But even here, there is tuning(or group shaping) potential with seating adjustments that are relatively small.
No problem.

Don't blow off seating!

Would that be 0.001 (a thousandth) or 0.0001 (a ten thousandth) of a grin??

 

[BlackEagle]

... and who can shoot and tell the difference on a target betwteen 0.002" and 0.003" off the lands?

 

[necchi]

Well, it's my understanding that this is what he's refering to;

the ogive-to-tail end length varies up to 6 thousandths!
I hope by this OP means OgvOAL to casehead, and NOT to bullet base.
If it is to bullet base then this thread falls apart so far,, and yes 6thou of variance as combined boat tail, bearing, with unqualified datums(ogive radius/boat tail angle) is utterly meaningless.

And that's why I have responded as I have.
Things are indeed tuff sometime in a forum venue, it's different than at the shop or at the range.
I can be a lousy "explainer" but I'm darn good at "show ya`"

And "datum" as it applies is only the point that his tools determine, my tool, even the same brand, unless set exactly the same as his, with exactly the same hole,, will select a different point of contact (datum) than his tools.
And with the Hornady tool, I can change that measurement simply by turning/rotating the insert in the caliper body attachment,, "datum" is only relative to the tool in your hand.

I have a very difficult time believing that the ogive from one 308 bullet in a single lot box is going to vary that much from another, bullet body length and the actual OAL of the bullet itself will vary, but the change in ogive curve??,, Not enough to matter.

 

[300 RUM]

Well, it's my understanding that this is what he's refering to;

the ogive-to-tail end length varies up to 6 thousandths!
I hope by this OP means OgvOAL to casehead, and NOT to bullet base.
If it is to bullet base then this thread falls apart so far,, and yes 6thou of variance as combined boat tail, bearing, with unqualified datums(ogive radius/boat tail angle) is utterly meaningless.

And that's why I have responded as I have.
Things are indeed tuff sometime in a forum venue, it's different than at the shop or at the range.
I can be a lousy "explainer" but I'm darn good at "show ya`"

And "datum" as it applies is only the point that his tools determine, my tool, even the same brand, unless set exactly the same as his, with exactly the same hole,, will select a different point of contact (datum) than his tools.
And with the Hornady tool, I can change that measurement simply by turning/rotating the insert in the caliper body attachment,, "datum" is only relative to the tool in your hand.

I have a very difficult time believing that the ogive from one 308 bullet in a single lot box is going to vary that much from another, bullet body length and the actual OAL of the bullet itself will vary, but the change in ogive curve??,, Not enough to matter.

I think i said .007" earlier , but I believe .005" tolerance is what hornady states for bullet ogive to bullet base

 

[Tuckerp229]

the ogive-to-tail end length varies up to 6 thousandths!
I hope by this OP means OgvOAL to casehead, and NOT to bullet base.
If it is to bullet base then this thread falls apart so far,, and yes 6thou of variance as combined boat tail, bearing, with unqualified datums(ogive radius/boat tail angle) is utterly meaningless.
[/quote]

The I realize that what I am looking for is consistent OAL and I am attempting to accomplish this via ogive measurement with a Hornady Bullet Comparator. I also realize that tips...especially polymer vary so using a bullet ogive comparator is more accurate than measuring off a bullet tip. Being frustrated as to where the variable was sourced I eventually just measured the actual Hornady SST bullet itself to see if I could discover where the variance was sourced. This immediately showed me that there were multiple locations for variance when measuring with the bullet comparator which meant that I had no way to discover nor solve the problem of varying OAL for my finished cartridges. I do realize that the bullet resides within the case once the cartridge has been assembled. This all led me to ask you all what I was missing.

I may have to try a different brand of bullets as suggested to find more consistency. Mikecr, JGB and Erik C. all suggested I look into Bob Green's reamer style caliper fixture for better measuring accuracy. Finally, I also am looking into the Wilson hand lathe trimmer given its renown for accuracy and as suggested, plan to turn the case around to true up the base since this is also a potential variable.


Now I have to go back, re-read to see what I have forgotten or missed from all of your posts.

Thank for the help!

 

[Tuckerp229]

Well I'll try to help a little.
My tools:
- Sinclair 'nut' bullet comparator: http://www.sinclairintl.com/.aspx/pid=34262/Product/Sinclair-Hex-Style-Bullet-Comparators
It's simple, free floating, and I use it for all logged values. It's just one of those tools that happens to work.
- Wilson micrometer top inline seating dies, with an arbor press: http://www.sinclairintl.com/.aspx/pid=39884/Product/Wilson-Sinclair-Hand-Die-Kit-w-Micro-Top
This is actually a less expensive system w/resp to quality threaded seating dies.
Again simple, free floating, precise adjustment, & positive stopping.
- Caliper: http://www.sinclairintl.com/.aspx/pid=41332/Product/Starrett-6-Electronic-Caliper
A less expensive caliper to .0005 works fine for this.
- As far as qualifying ogive radius, I use Bob Green comparators: http://greensrifles.com/New_Products.html
I also use a purpose built taper mic w/software to determine actual ogive radius(for BC calcs). But Bob's comparator provides a quick check of many bullets.

I also use wilson bushing neck dies(some custom), and Sinclair expander mandrels, to produce ~1thou of neck tension with semi-cleaned(carbon remaining) unlubed necks. I do not anneal until it's actually needed. With this, I have low seating forces that do not create wedging of the seater plug against noses.

For seating with a threaded press extra factors can muddle things up a bit. Mostly play in the press. I would use a micrometer type die & bottom the die to the shellholder for seating & may or may not cam-over. Depends on results.
Like mentioned there are many threads here to improve seating with this.

As stated I am using the Hornady bullet comparator...I read about the Sinclair nut and cannot see if it would be an improvement..the Bob Green reamer style seems to be a solid improvement though.

I did open my wallet and buy the LE Wilson in line dies for my 6.5 swede. that is how I got into this mess...ignorance had been bliss. Wilson didn't make the micrometer top for the Swede so I added Sinclair's micrometer to it.

I bought the K&M arbor press with dial gauge.

I also use K&M's neck turning hand lathe and am turning the necks for uniform wall thickness.

I use the LE Wilson neck bushings

Calipers...holy hanna, I have two digital s and because I discovered the OAL variance I believed them to be faulty of low on batteries so I popped for Starett calipers.

Your statement:"I also use wilson bushing neck dies(some custom), and Sinclair expander mandrels, to produce ~1thou of neck tension with semi-cleaned(carbon remaining) unlubed necks. I do not anneal until it's actually needed. With this, I have low seating forces that do not create wedging of the seater plug against noses."

Low seating forces intrigues me I thought one needed 2-3 th of undersize pressure for good neck tension. Do you multi load or always insert one cartridge into your rifle at a time?

As I said in my previous post I am looking into The Wilson trimming lathe and Bob Green's reamer style case holder fixture for the calipers. Just hoping I'll finally be at an end of the buying and seeing some dramatic improvements.

 

[6BRinNZ]

Low seating forces intrigues me I thought one needed 2-3 th of undersize pressure for good neck tension. Do you multi load or always insert one cartridge into your rifle at a time?

IMO - high neck tension is a large contributor to seating variances, along with neck thickness variations and poor seating technique. By using .001 - .0015" neck tension and controlling the other two I expect to be +- .001" seating depth before sorting bullets (A-maxes). I measure every single round I fire. Bullet sorting IMO brings into alignment the last .001 - .002 of variation.

I have also found annealing to be conducive to consistent seating depths, however IMO the effectiveness of this is dependant on chamber specs, so YMMV.

To support one of my statements have a read of the thread listed below.

http://forum.accurateshooter.com/index.php?topic=3783184.0

 

[necchi]

Ya know,
In all of this we kinda missed the bottom line.
What are you shooting?
and ,
What kind of groups are you getting now?

 

[AP2020]

..I picked up a Sinclair Bullet Sorting Stand back in 2010,

[I already had the dial indicator] when they first came out several months ago....so far my "failure rate" is about 7 out of 100 bullets that have a greater than +/- 0.001" base to ogive dimension.

..I, too may be anal about my reloading...but at least I know when I miss it was either me or the WIND!!


Here is the TYPICAL "pass" bullet:

Here is the TYPICAL "reject" bullet:

 

[Erik Cortina]

I don't see what you gain by sorting base to ogive. Neither of those two points are contact points. One is centered (hopefully) in barrel (ogive) not touching anything and the other is inside case, also not touching anything (bullet base).

 

[mikecr]

6.5x61Super I don't know if you read through this thread, or others related. But if you did, you should suspect that your Buhay tool measurement is meaningless.

You're comparing combined variance in base length+/-bearing+/-ogive radius.
With this combination you can't determine if your measures matching actually mean the bullets match, nor if measured variance indicates a specific mis-match.
You don't know which is what as they aren't isolated measurements.
And can you determine the affects of each parameter individually & then combined?

That 4thou variance could be +5thou base length AND -7thou bearing AND +1/4cal in ogive radius,, all combining to mean nothing directly w/regard to seating depths, and internal/external ballistics.
It's tail chasing, and while it don't hurt to cull bullets as you're measuring, you're not gaining a thing in doing so.

 

[AP2020]

6.5x61Super I don't know if you read through this thread, or others related. But if you did, you should suspect that your Buhay tool measurement is meaningless.

You're comparing combined variance in base length+/-bearing+/-ogive radius.
With this combination you can't determine if your measures matching actually mean the bullets match, nor if measured variance indicates a specific mis-match.
You don't know which is what as they aren't isolated measurements.
And can you determine the affects of each parameter individually & then combined?

That 4thou variance could be +5thou base length AND -7thou bearing AND +1/4cal in ogive radius,, all combining to mean nothing directly w/regard to seating depths, and internal/external ballistics.
It's tail chasing, and while it don't hurt to cull bullets as you're measuring, you're not gaining a thing in doing so.

okay Mike, I just re-read the entire thread carefully!

My intentions with the comparator were to sort bullets before I used a Whidden pointer and trimmer, apparently I have been mis-guided!


I spoke with Walt Berger several years ago....typically the causes of varying ogive measurements can be traced back to new, versus older/worn dies in the bullet making process.....

I have re-loaded for 23 years now, learning everyday. I rememebr back "in the day", before I had money to spend, I would wonder why my .243 COL would vary +/- 0.003" with Sierra Varminters....not until later on did I "realize" that varying bullet lengths were a possibility.

What, if any good is the Sinclair comparator, Buhay, etc......aside from sorting base to ogive measurements...

Thanks!

 

[AP2020]

...from my understanding....a more meaningful dimension would be the start of the bearing surface to the rifling, but how would you arrive at this measurement when sorting bullets AND seating bullets....