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Max Online: 16728 @ 03/25/12 08:51 AM
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#7155430 - 04/30/18 08:55 AM Reloading Manual Data....Why, COAL?
Jgraider Online   content
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Registered: 06/13/15
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Loc: West Texas
There's probably an obvious reason, but I admittedly don't get it. Let's take the Nosler 6.5 Creedmoor on line load data, for example., but it's probably true of any of them. How do they determine what seating depth they test their bullets? They never seat them out to max SAAMI lengths. Surely they're not testing various lengths and publishing the most accurate. I'm one of those reloaders who always starts out loads at max mag length, or .010 off.

Why do these manufacturers do this?

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#7155435 - 04/30/18 08:58 AM Re: Reloading Manual Data....Why, COAL? [Re: Jgraider]
Dave3575 Offline
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simply because they have to pick something and they go with the law of averages. (mag length, SAMMI reamer spec, etc)

This is from accuratepowder.com

SPECIAL NOTE ON CARTRIDGE OVERALL LENGTH “COL”
It is important to note that the SAAMI “COL” values are for the firearms and ammunition manufacturers industry and must be seen as a guideline only. The individual reloader is free to adjust this dimension to suit their particular firearm-component-weapon combination. This parameter is determined by various dimensions such as 1) magazine length (space), 2) freebore-lead dimensions of the barrel, 3) ogive or profile of the projectile and 4) position of cannelure or crimp groove.


Edited by Dave3575 (04/30/18 08:59 AM)

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#7155460 - 04/30/18 09:28 AM Re: Reloading Manual Data....Why, COAL? [Re: Jgraider]
kmon1 Online   content
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Registered: 09/27/06
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SAAMI exhists as an industry standards orginization and part of those standards are chamber and loaded round dimensions. Loaded cartridge max dimensions are usually a little smaller than min chamber dimensions so all ammo will work in all chambers or that is the plan.
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#7155461 - 04/30/18 09:29 AM Re: Reloading Manual Data....Why, COAL? [Re: Jgraider]
kmon1 Online   content
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You can find the min and max dimensiins along with lots more info at SAAMI.org
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#7155473 - 04/30/18 09:39 AM Re: Reloading Manual Data....Why, COAL? [Re: Jgraider]
Jgraider Online   content
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I totally get rationale about SAAMI standards and specsand am somewhat familiar with it. I was really wondering why, for instance, if again looking at 6.5CM data regarding 130gr bullets. Why would Nosler load those at 2.775 COAL, when the SAAMI spec is 2.825? Since SAAMI spec is the spec every manufacturer goes by and every factory chamber should chamber a round within those specs....why would load data be tested at such short COAL's?

I don't think I asked the question very well the first time.

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#7155491 - 04/30/18 09:57 AM Re: Reloading Manual Data....Why, COAL? [Re: Jgraider]
ckat Offline
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Some of it may have to do with the bearing surface of each bullet design??? The bullet needs to be seated where there is enough neck tension to reliably hold that bullet. Some bullet designs don't allow for max COAL and save enough bearing surface in the neck area...

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#7155695 - 04/30/18 01:48 PM Re: Reloading Manual Data....Why, COAL? [Re: Jgraider]
kmon1 Online   content
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Registered: 09/27/06
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Yes bullet shape does come into play, the ogive shape makes a difference. You can seat a VLD type bullet to a longer length than say a round nose bullet.
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#7155715 - 04/30/18 02:24 PM Re: Reloading Manual Data....Why, COAL? [Re: kmon1]
TackDriver Online   content
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Registered: 05/02/14
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Originally Posted By: kmon1
Yes bullet shape does come into play, the ogive shape makes a difference. You can seat a VLD type bullet to a longer length than say a round nose bullet.


I agree.

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#7155755 - 04/30/18 03:01 PM Re: Reloading Manual Data....Why, COAL? [Re: TackDriver]
Jgraider Online   content
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Originally Posted By: TackDriver
Originally Posted By: kmon1
Yes bullet shape does come into play, the ogive shape makes a difference. You can seat a VLD type bullet to a longer length than say a round nose bullet.


I agree.



I agree too, which makes the Nosler load data even more baffling. They have the tested loads for the 129 LRAB, a long bullet, at 2.775 OAL.....?

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#7155784 - 04/30/18 03:37 PM Re: Reloading Manual Data....Why, COAL? [Re: Jgraider]
ChadTRG42 Offline
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It has to do with the ogive location of the bullet. Some bullets have a shorter ogive to tip length, which will cause a shorter coal.
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#7155836 - 04/30/18 04:27 PM Re: Reloading Manual Data....Why, COAL? [Re: ChadTRG42]
Jgraider Online   content
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Originally Posted By: ChadTRG42
It has to do with the ogive location of the bullet. Some bullets have a shorter ogive to tip length, which will cause a shorter coal.


Ohhhhh. Never would have thought of that. So Chad, if you don't mind.....when you're loading your custom ammo, how do you know what length to set COAL?

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#7156553 - 05/01/18 10:00 AM Re: Reloading Manual Data....Why, COAL? [Re: Jgraider]
ChadTRG42 Offline
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Almost 100% of the time I load to an ogive. There's a sweet spot where you want to be on most rounds. But it also depends on the rifle. For example, if a customer brings me a Browning A-bolt in say, a 300 Win Mag, I know I won't be able to use an aggressive VLD type bullet. The magazine box that the A-bolt's use are way too short, and only have a max COAL of about 3.340". So selecting a VLD type bullet would seat the bullet REALLY deep in the case (and have less room for powder) and have a long jump to the rifling (if feeding out of the mag). This would generally not allow it to shoot as good. We would select a tangent ogive bullet, or a bullet that can tolerate a jump and still shoot well. On the other hand, if the rifle is a 300 WM and we are using an AI DBM (Accuracy International, Detachable Box Mag), I know I have about 3.700" COAL of room in the mag. I can get most any bullet seated close to or touching the lands, and still fit and feed out of the mag. This is why on some of my ammo on my website I list the COAL, so the shooter knows it's loaded out long and won't fit in some rifles.

It's different from bullet to bullet. Some bullets have a short ogive to tip length, and others have a much longer ogive to tip length. Also, some bullets will shoot better having a larger jump to the rifling than others. The LR AB like a jump, and won't (generally) shoot as good on the lands.

You have to understand about ogive's to load ammo correctly. I've seen multiple reloaders load their ammo to the same COAL when they switch bullets and not understand why their new bullet is jamming into the lands and they can't close the bolt.

I've used this picture several times. It's a simple picture that explains the difference. Adding a polymer tip generally lengthens the COAL, depending on the ogive to tip length and if the bullet is a secant or tangent ogive.

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#7156585 - 05/01/18 10:20 AM Re: Reloading Manual Data....Why, COAL? [Re: Jgraider]
pertnear Online   content
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Registered: 12/31/14
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Great picture ChadTRG42. A picture is worth a 1000 words....Thanks
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#7157680 - 05/02/18 10:50 AM Re: Reloading Manual Data....Why, COAL? [Re: Jgraider]
SenderoTaxi Offline
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Registered: 10/06/10
Posts: 204
Loc: Round Rock
Originally Posted By: Jgraider
I totally get rationale about SAAMI standards and specsand am somewhat familiar with it. I was really wondering why, for instance, if again looking at 6.5CM data regarding 130gr bullets. Why would Nosler load those at 2.775 COAL, when the SAAMI spec is 2.825? Since SAAMI spec is the spec every manufacturer goes by and every factory chamber should chamber a round within those specs....why would load data be tested at such short COAL's?

I don't think I asked the question very well the first time.


Real world example you gave, so real world application:

My 6.5 Creedmoor magazines measure 2.810. I leave .010 just to make sure i don't jam anthing, so i load my rounds at 2.800 or less.
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