Variance in lengths of OAL when DIE is same

Reloading equipment, methods, load data, powder and projectile information.

Variance in lengths of OAL when DIE is same

Post by TassieTiger » 21 Dec 2018, 5:57 pm

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.
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Re: Variance in lengths of OAL when DIE is same

Post by bladeracer » 21 Dec 2018, 6:00 pm

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.


If you are measuring to the point of the bullet this is totally normal.
The seating die knows nothing about the point of the bullet, it grips the bullet somewhere down the ogive depending on the die and bullet design.
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Re: Variance in lengths of OAL when DIE is same

Post by TassieTiger » 21 Dec 2018, 7:02 pm

In that respect coal means very little then?
Where do people measure too to ensure 100% consistency?
Tikka T3 .260 (custom)
Steyr Pro Varmint .223
CZ455 .22 & Norinco .22
ATA 686 U/O 12g & Baikal S/S 12g
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Sauer 100 30-06
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Re: Variance in lengths of OAL when DIE is same

Post by Ziad » 21 Dec 2018, 7:14 pm

Get a bullet measure...or be happy
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Re: Variance in lengths of OAL when DIE is same

Post by Wm.Traynor » 21 Dec 2018, 7:23 pm

COAL is only the measurement from base to tip. It is relevant if the ammo is to in fit a magazine, in which case (NPI) you might want to make it 0.030" or 3/4 mm shorter to guarantee an easy fit. If target shooting, you forget about magazine fire and load bullets according to where the ogive is located. Just reading about that process was enough to put me off for life. Good luck whatever way you decide to go go.
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Re: Variance in lengths of OAL when DIE is same

Post by brett1868 » 21 Dec 2018, 7:57 pm

Swaged projectiles are not necessarily precise and the distance from Meplat to Ogive to Base with vary more then you may realise. The way I deal with this is to spend BS amounts of time preparing projectiles by pointing then trimming the Meplat for a uniform Ogive to Meplat then I sort and batch by measuring the base to Ogive before then sub batching by weight. When it comes to loading I use an Ogive gauge and micrometer seating die, seat long - measure then adjust and reseat before backing the die off and starting again.
Last edited by brett1868 on 21 Dec 2018, 9:38 pm, edited 1 time in total.
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Re: Variance in lengths of OAL when DIE is same

Post by marksman » 21 Dec 2018, 8:03 pm

Wm.Traynor wrote:COAL is only the measurement from base to tip. It is relevant if the ammo is to in fit a magazine, in which case (NPI) you might want to make it 0.030" or 3/4 mm shorter to guarantee an easy fit. If target shooting, you forget about magazine fire and load bullets according to where the ogive is located. Just reading about that process was enough to put me off for life. Good luck whatever way you decide to go go.


this is the right information :thumbsup:

you need to measure from the ogive for consistency
it is also necessary to measure projectiles before seating from the base to the ogive, you may see big differences with some brands

if you cant be bothered with that either jump big or jam
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Re: Variance in lengths of OAL when DIE is same

Post by SCJ429 » 21 Dec 2018, 8:08 pm

The easy cheap way is to get some Hornady bullet comparators and bolt it to you verniers. As Brett said earlier, you would need to batch your projectiles prior to loading if you are wanting to keep the COAL consistant. If you don't want to do this then buy Bergers which are unbelievably consistant. Or Lapua Secnars.
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Re: Variance in lengths of OAL when DIE is same

Post by bladeracer » 21 Dec 2018, 8:26 pm

TassieTiger wrote:In that respect coal means very little then?
Where do people measure too to ensure 100% consistency?


It means it'll feed in your magazine.
If you are trying to get a consistent bullet jump, then you need to take your measurement at the point where the bullet meets the rifling, usually around 8-thou under groove diameter.
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Re: Variance in lengths of OAL when DIE is same

Post by Oldbloke » 21 Dec 2018, 8:41 pm

SCJ429 wrote:The easy cheap way is to get some Hornady bullet comparators and bolt it to you verniers. As Brett said earlier, you would need to batch your projectiles prior to loading if you are wanting to keep the COAL consistant. If you don't want to do this then buy Bergers which are unbelievably consistant. Or Lapua Secnars.


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Re: Variance in lengths of OAL when DIE is same

Post by TassieTiger » 21 Dec 2018, 8:42 pm

I was loading some 260’s and had everything set perfect - 71.95mm plus or minus maybe .1 mm.
I then ran my box of projectiles empty so I opened up another box of exactly the same 120gn Nosler ballistic hunting and first couple measured 71.60 and then a couple at 72.00mm....

Some comparators are on their way.
Thanks.
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Re: Variance in lengths of OAL when DIE is same

Post by TassieTiger » 21 Dec 2018, 8:56 pm

brett1868 wrote:Swaged projectiles are not necessarily precise and the distance from Meplat to Ogive to Base with vary more then you may realise. The way I deal with this is to spend BS amounts of time preparing projectiles by pointing then trimming the Meplat for a uniform Ogive to Meplat then I sort and batch by measuring the base to Meplat before then sub batching my weight. When it comes to loading I use an Ogive gauge and micrometer seating die, seat long - measure then adjust and reseat before backing the die off and starting again.


Please help stop me from catching this disease... lol
Tikka T3 .260 (custom)
Steyr Pro Varmint .223
CZ455 .22 & Norinco .22
ATA 686 U/O 12g & Baikal S/S 12g
Steyr Pro Hunt 30-06 (Dud!!!)
Sauer 100 30-06
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Re: Variance in lengths of OAL when DIE is same

Post by bigrich » 21 Dec 2018, 9:20 pm

strange tas. i have a preferance for nosler projectiles these days and i don't get a lot of variance in COAL . i have a hornady press too. i like hornady products, always well made and no fuss, but i think nosler projectiles are where it's at for me. nosler 50 bt's for my 222, nosler 120 bt's for my 6.5x55 , superb accuracy. my 308 however loves 165 speer spbt . cheap too :drinks: :thumbsup:
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Re: Variance in lengths of OAL when DIE is same

Post by brett1868 » 21 Dec 2018, 9:42 pm

TassieTiger wrote:
brett1868 wrote:Swaged projectiles are not necessarily precise and the distance from Meplat to Ogive to Base with vary more then you may realise. The way I deal with this is to spend BS amounts of time preparing projectiles by pointing then trimming the Meplat for a uniform Ogive to Meplat then I sort and batch by measuring the base to Meplat before then sub batching my weight. When it comes to loading I use an Ogive gauge and micrometer seating die, seat long - measure then adjust and reseat before backing the die off and starting again.


Please help stop me from catching this disease... lol


Easily cured by using precision CNC machined solid copper or brass projectiles. The only projectiles I bother to prep are the 350gr SMK's I run in the Cheytac cause every little bit matters at 1600m :)
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Re: Variance in lengths of OAL when DIE is same

Post by Stix » 22 Dec 2018, 7:38 am

TassieTiger wrote:Please help stop me from catching this disease... lol


Nah mate...too late...you're gone...!!!

You were standing too close to the tracks when the shooters OCD train passed by & jagged your shirt & hooked you up... :clap:

Your denial is just due to your head hitting a few sleepers while being dragged along before we saved you & pulled you aboard the carriage... :lol:

Go & open a dedicated shooting fund trust account...you're gonna need it...!!! :thumbsup:

Welcome aboard... :drinks:
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Re: Variance in lengths of OAL when DIE is same

Post by bigrich » 22 Dec 2018, 8:31 am

Stix wrote:
TassieTiger wrote:Please help stop me from catching this disease... lol


Nah mate...too late...you're gone...!!!

You were standing too close to the tracks when the shooters OCD train passed by & jagged your shirt & hooked you up... :clap:

Your denial is just due to your head hitting a few sleepers while being dragged along before we saved you & pulled you aboard the carriage... :lol:

Go & open a dedicated shooting fund trust account...you're gonna need it...!!! :thumbsup:

Welcome aboard... :drinks:


no doubt about it stix, your a card :D :drinks: :thumbsup:
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Re: Variance in lengths of OAL when DIE is same

Post by Ziad » 22 Dec 2018, 9:26 am

I send condolences to your family they knew a good maybe even a little rich fella.... but now they only see a broke fella. Atleast you might be happy
Blame it on the phone auto correct
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Re: Variance in lengths of OAL when DIE is same

Post by Stix » 22 Dec 2018, 3:09 pm

bigrich wrote:
Stix wrote:
TassieTiger wrote:Please help stop me from catching this disease... lol


Nah mate...too late...you're gone...!!!

You were standing too close to the tracks when the shooters OCD train passed by & jagged your shirt & hooked you up... :clap:

Your denial is just due to your head hitting a few sleepers while being dragged along before we saved you & pulled you aboard the carriage... :lol:

Go & open a dedicated shooting fund trust account...you're gonna need it...!!! :thumbsup:

Welcome aboard... :drinks:


no doubt about it stix, your a card :D :drinks: :thumbsup:


Gees...ive been called plenty of things starting with the letter 'see' ( :lol: ) "C"...

Bet a card..??....well thats a new one...!!

Ill pretend its a good thing... :D
The man who knows everything, doesnt really know everything...he's just stopped learning...
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