Variance in lengths of OAL when DIE is same

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Re: Variance in lengths of OAL when DIE is same

Post by pomemax » 22 Dec 2018, 3:37 pm

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Re: Variance in lengths of OAL when DIE is same

Post by straightshooter » 25 Dec 2018, 7:01 am

TassieTiger wrote:How come, I can set my die up for a COAL of say 79.00mm and then without changing a single thing, on the die or on the press or anything - I can get 78.70 to say 79.10 to 78.60 to 79.00 ? This is with the cases exactly the same lenght - each one measured with verniers and cut to length.
Even with brand new Lapua brass - which is quite remarkable, I end up with different oals.
Is this difference in the ogive of the projectile ?

I have noticed that my Hornady press, has a slight bit of movement in the collet and in the press itself it seems to be a tiny amount of movement and I know we are talking very small numbers but when trying to get the COAL exactly perfect, its frustrating to chase numbers back and forth...

Cheers. Tas.


As others have pointed out there is some variation in ogive position even in high quality projectiles.
You need to have a reliable method of establishing oal when the projectile's ogive starts into the lands.
Method 1 is to size the neck of an empty case just enough so that the projectile can be seated long and it is firmly held but not so tight that it can't be moved. Chamber the test case and force the bolt closed. Then remove the case. Measure oal.
Now this is the most important step. Use that same particular projectile to set up your seating die for your desired projectile throat relationship.
Method 2 is quicker and simpler. Use a Stoney Point Chamber All gauge for establishing your maximum oal. Hornady now make a copy at a reasonable price. Measure your resulting oal.
And again the most important step is to use that exact same projectile to set up your seating die.
From there on you can ignore the minor variations in COAL particularly so if your seating stem makes contact with your projectile's ogive near to it's maximum diameter and not near the tip.
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Re: Variance in lengths of OAL when DIE is same

Post by bigrich » 25 Dec 2018, 8:56 am

pomemax wrote:'no doubt about it stix, your a card '(NEED DEALING with )


it's a old saying from gambling/card playing . it's a reference to there's a joker card in every deck of cards :lol: :lol: :lol:

:drinks: :drinks: merry x-mas :drinks: :drinks: :thumbsup:
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Re: Variance in lengths of OAL when DIE is same

Post by TassieTiger » 25 Dec 2018, 9:56 am

straightshooter wrote:
TassieTiger wrote:How come, I can set my die up for a COAL of say 79.00mm and then without changing a single thing, on the die or on the press or anything - I can get 78.70 to say 79.10 to 78.60 to 79.00 ? This is with the cases exactly the same lenght - each one measured with verniers and cut to length.
Even with brand new Lapua brass - which is quite remarkable, I end up with different oals.
Is this difference in the ogive of the projectile ?

I have noticed that my Hornady press, has a slight bit of movement in the collet and in the press itself it seems to be a tiny amount of movement and I know we are talking very small numbers but when trying to get the COAL exactly perfect, its frustrating to chase numbers back and forth...

Cheers. Tas.


As others have pointed out there is some variation in ogive position even in high quality projectiles.
You need to have a reliable method of establishing oal when the projectile's ogive starts into the lands.
Method 1 is to size the neck of an empty case just enough so that the projectile can be seated long and it is firmly held but not so tight that it can't be moved. Chamber the test case and force the bolt closed. Then remove the case. Measure oal.
Now this is the most important step. Use that same particular projectile to set up your seating die for your desired projectile throat relationship.
Method 2 is quicker and simpler. Use a Stoney Point Chamber All gauge for establishing your maximum oal. Hornady now make a copy at a reasonable price. Measure your resulting oal.
And again the most important step is to use that exact same projectile to set up your seating die.
From there on you can ignore the minor variations in COAL particularly so if your seating stem makes contact with your projectile's ogive near to it's maximum diameter and not near the tip.


Even when I set up my max / demo cartridge- I’d place it into my press to set up die and I’d screw die down to touch nose and it would creep projectile in .5mm or similar as when I’m tightening the screw, I can’t feel it until it’s touching and this touch on a loose case...hmmm...so another method needs to be found for me...which is why I’ve bought the hornady comparator. Hopefully, I don’t end up weighing individual parts, turning necks, triple measuring everything, etc like Brett...because my family WILL divorce me.
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Re: Variance in lengths of OAL when DIE is same

Post by bladeracer » 25 Dec 2018, 1:04 pm

TassieTiger wrote:Even when I set up my max / demo cartridge- I’d place it into my press to set up die and I’d screw die down to touch nose and it would creep projectile in .5mm or similar as when I’m tightening the screw, I can’t feel it until it’s touching and this touch on a loose case...hmmm...so another method needs to be found for me...which is why I’ve bought the hornady comparator. Hopefully, I don’t end up weighing individual parts, turning necks, triple measuring everything, etc like Brett...because my family WILL divorce me.


You could tap a thread in the flash hole and thread in a screw to prevent the bullet from moving back into the case. Or drill out the primer pocket and fill the case with epoxy behind the bullet.

Personally I just set up the seating die every time by seating a bullet, measuring OAL, adjusting to suit. I use lots of different bullets so I'm always adjusting the dies. On the Lee dies, the thread pitch is 1.5mm, so a full turn is .059", I round it to 60-thou. A quarter-turn is 15-thou and so on. If your measurement is 2.531" and you're chasing 2.475", you need 56-thou, or almost one full turn.
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Re: Variance in lengths of OAL when DIE is same

Post by bladeracer » 25 Dec 2018, 1:10 pm

straightshooter wrote:Method 1 is to size the neck of an empty case just enough so that the projectile can be seated long and it is firmly held but not so tight that it can't be moved. Chamber the test case and force the bolt closed. Then remove the case. Measure oal.


The problem with this method comes when you're seating close to the lands. Measuring overall length to the point of the bullet can leave enough difference at the ogive (where it meets the rifling) to have some bullets jammed, and others well off the lands.

Unless your seating stem touches the bullet along the ogive at the bore diameter (at .300" on a .308" bullet) you will have to make fine adjustments to every round anyway using an ogive comparator. If you're seating more than about 20-thou off the lands I doubt it matters outside of serious competition.
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Re: Variance in lengths of OAL when DIE is same

Post by marksman » 25 Dec 2018, 3:49 pm

if your seating stem is pushing the bullet from the tip it needs to be drilled out so that it only connects at the ogive to give a true reading
maybe this is the problem :unknown:
but you measure the loaded round from the ogive to the base for a true measurement, this is what you use the comparator for
if they wont fit your mag because some are longer than others seat them shorter so they will but at the same oal from base to ogive
when you measure max oal you do it with your firing pin removed and with a fired in that chamber case
it's up to you if you dont or you do but if not you are just playing around
Bretts advise is good advise for solving your problem :thumbsup: :drinks:
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Re: Variance in lengths of OAL when DIE is same

Post by Oldbloke » 25 Dec 2018, 4:44 pm

"when you measure max oal you do it with your firing pin removed and with a fired in"

Why? How would the firing pin interfere if it's cocked?
No safety reason, it's an empty case.
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Re: Variance in lengths of OAL when DIE is same

Post by TassieTiger » 25 Dec 2018, 5:28 pm

marksman wrote:if your seating stem is pushing the bullet from the tip it needs to be drilled out so that it only connects at the ogive to give a true reading
maybe this is the problem :unknown:

Bretts advise is good advise for solving your problem :thumbsup: :drinks:


How could you tell where the seating die is touching on a projectile? Smoke it with carbon or ?
I assumed it would be grasping it on the ogive but where would be a guess...
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Re: Variance in lengths of OAL when DIE is same

Post by marksman » 25 Dec 2018, 5:55 pm

Oldbloke wrote:"when you measure max oal you do it with your firing pin removed and with a fired in"

Why? How would the firing pin interfere if it's cocked?
No safety reason, it's an empty case.


Oldbloke who said there was a safety issue :unknown:
you do it this way so you do not have any interference and can see when the bolt just closes without any interference from the firing pin spring
so make a dummy round longer than will fit your chamber, then reduce the oal bit by bit till the bolt just closes, there is your perfect max oal
does not work properly without using a case fired in the chamber of the rifle, you will not see the same results without taking the firing pin out of the bolt
this way the bolt handle falls on its own weight, simples

to check if your seating stem is right for your projectile shape take it out and try a projectile in it if it does not touch at the ogive it is hitting the point :drinks:
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Re: Variance in lengths of OAL when DIE is same

Post by bladeracer » 25 Dec 2018, 7:54 pm

marksman wrote:to check if your seating stem is right for your projectile shape take it out and try a projectile in it if it does not touch at the ogive it is hitting the point :drinks:


Mine touch at different points along the ogive depending on the shape of the bullet. None of my dies seat on the point of the bullet, or at point where the ogive meets the rifling. It's generally about halfway between the two points.
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Re: Variance in lengths of OAL when DIE is same

Post by marksman » 25 Dec 2018, 9:28 pm

bladeracer wrote:
marksman wrote:to check if your seating stem is right for your projectile shape take it out and try a projectile in it if it does not touch at the ogive it is hitting the point :drinks:


Mine touch at different points along the ogive depending on the shape of the bullet. None of my dies seat on the point of the bullet, or at point where the ogive meets the rifling. It's generally about halfway between the two points.


what I meant blade is that if your projectile swims around the ogive and you can see it is bottoming out on the tip of the projectile you will have problems in oal differences but the simple fix is to drill out the inside of the seater stem so the tip will not bottom out and the seater sits on the ogive or wherever on the bullet so the seater does not push the bullet from the tip causing irregularities in length. it is also a very good idea to polish the inside of the seater stem

if this is a problem you can always buy a vld seater stem but this is really all that is needed :drinks: make the hole in the seater stem deeper :thumbsup:
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Re: Variance in lengths of OAL when DIE is same

Post by Bills Shed » 26 Dec 2018, 7:40 am

It is nice to get a consistent COL and as stated measuring the tip to base is not going to do it for you. If shooting paper go crazy, if for the field, it needs to work in a magazine and that is the governing factor. You can get really wrapped around the axles trying to get the perfect round but the paddock is the great equaliser. Humans are more inaccurate than your rifle.

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Re: Variance in lengths of OAL when DIE is same

Post by FoxSpotter » 26 Jan 2019, 6:37 pm

Hi..
I've similar problem with seating depth...seems related to pressure applied to press arm once it's come to a stop...on an old Lee press...
Using a Forster micro seating die...thinking a Cam over type press might eliminate this..
Using hornady comparator..variations up to 5 thou approx...
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