c.o.a.l

sako2 · April 18, 2009, 04:09 AM

I'm reloading for my rifle's and i'm having problem's getting consistent c.o.a.l measurement's. I'm using a rcbs rock chucker press and rcbs dies what should i look for.

Sevens · April 18, 2009, 07:36 AM

I have found that erratic COAL is most often caused by a bullet shape that doesn't really "jive" with the shape of the seater plug inside the die. I wouldn't say this happens often with rifle rounds, which are pretty close to the same general shape.

Is there a chance you are expecting too much in your measurements? How much variance are you seeing?

freakshow10mm · April 18, 2009, 07:37 AM

Is your bullet seating die lock ring firmly tightened? Sometimes that can be loose and cause variation. An OAL variance of .050" or so isn't much to sneeze at. I don't know what your variance is.

amamnn · April 18, 2009, 01:25 PM

Have you actually measured the base to tip and base to ogive of the bullets? Depending on the brand, your box of bullets might have been loaded with bullets from as many as 5 different dies; sometimes this can give your seater fits.

jaybird.78 · April 18, 2009, 03:48 PM

I have been using Hornady HPBT match bullets in my .308 and the tips of these bullets are not uniform. Hence I get small inconsistencies with total length. The rifle doesn't seem to mind and so I don't seem to mind.

Good luck

dmazur · April 18, 2009, 05:38 PM

Hornady makes a bullet comparator that sells for around $30 or so. You use it with calipers to measure the distance from the base of the cartridge to the bullet ogive. (The basic kit includes a few inserts for common calibers like .223, .243 and .308 but Hornady makes inserts for just about every caliber.)

I've been fighting COAL measurement for quite a while now. I think what I'm going to do is measure to bullet tip, as that's what's published in the load data, but make sure I record the ogive distance in my log. (So I can repeat it.)

I think the bullet seating die pushes on the ogive, so variations at the bullet tip probably don't affect seating depth. The variations just drive you crazy if you think your seating depth is varying.

Even match bullets vary a little in length, and I think "ordinary" bullets vary more.

sako2 · April 19, 2009, 06:44 AM

I'm probably expecting to much it's .010 in variation. Thank's for the help.

Nnobby45 · April 19, 2009, 07:09 AM

Variations are common, especially with HP's, including HP match ammo. .005 or even more wouldn't be unusual. If the ogives are not exactly the same, that can do it, and so can the tips where the fold comes together--such as .30 cal. 168 match ammo

Some good hunting ammo, like Swift Scirocco's vary by, oh, maybe .005 to .007.

Don't worry about it. If the bullets are the same, then your seating plug will contact the bullets uniformly in the same place.

Measure the differences in the over all bullets lengths. That will prove informative.

Then measure the difference in the loaded rounds. If the COL variation is different than the bullet variation, then maybe differences in the ogive as well as in the bullet contribute. If the ogives are different, the seating cup makes contact on different parts of the bullet, and that changes the COL.

What's important is how things look on paper at the range. Consistency in the center of gravity (concentricity) is more important than the minor variations we've been discussing.

April 18, 2009, 04:09 AM	#1
sako2 Senior Member Join Date: April 12, 2009 Posts: 741	c.o.a.l I'm reloading for my rifle's and i'm having problem's getting consistent c.o.a.l measurement's. I'm using a rcbs rock chucker press and rcbs dies what should i look for.

April 18, 2009, 07:36 AM	#2
Sevens Senior Member Join Date: July 28, 2007 Location: Ohio Posts: 11,756	I have found that erratic COAL is most often caused by a bullet shape that doesn't really "jive" with the shape of the seater plug inside the die. I wouldn't say this happens often with rifle rounds, which are pretty close to the same general shape. Is there a chance you are expecting too much in your measurements? How much variance are you seeing? __________________ *Attention Brass rats and other reloaders:* I really need .327 Federal Magnum brass, no lot size too small. Tell me what caliber you need and I'll see what I have to swap. PM me and we'll discuss.

April 18, 2009, 01:25 PM	#4
amamnn Senior Member Join Date: May 13, 2006 Location: WA, the left armpit of the USA Posts: 1,323	Have you actually measured the base to tip and base to ogive of the bullets? Depending on the brand, your box of bullets might have been loaded with bullets from as many as 5 different dies; sometimes this can give your seater fits. __________________ "If the enemy is in range, so are you." - Infantry Journal

April 18, 2009, 05:38 PM	#6
dmazur Senior Member Join Date: July 5, 2007 Location: Pacific NW Posts: 1,310	Hornady makes a bullet comparator that sells for around $30 or so. You use it with calipers to measure the distance from the base of the cartridge to the bullet ogive. (The basic kit includes a few inserts for common calibers like .223, .243 and .308 but Hornady makes inserts for just about every caliber.) I've been fighting COAL measurement for quite a while now. I think what I'm going to do is measure to bullet tip, as that's what's published in the load data, but make sure I record the ogive distance in my log. (So I can repeat it.) I think the bullet seating die pushes on the ogive, so variations at the bullet tip probably don't affect seating depth. The variations just drive you crazy if you think your seating depth is varying. Even match bullets vary a little in length, and I think "ordinary" bullets vary more. __________________ .30-06 Springfield: 100 yrs + and still going strong

April 18, 2009, 07:37 AM	#3
freakshow10mm Junior member Join Date: January 23, 2008 Location: MI Posts: 1,398	Is your bullet seating die lock ring firmly tightened? Sometimes that can be loose and cause variation. An OAL variance of .050" or so isn't much to sneeze at. I don't know what your variance is.

April 18, 2009, 03:48 PM	#5
jaybird.78 Junior Member Join Date: April 11, 2009 Posts: 13	I have been using Hornady HPBT match bullets in my .308 and the tips of these bullets are not uniform. Hence I get small inconsistencies with total length. The rifle doesn't seem to mind and so I don't seem to mind. Good luck

April 19, 2009, 06:44 AM	#7
sako2 Senior Member Join Date: April 12, 2009 Posts: 741	I'm probably expecting to much it's .010 in variation. Thank's for the help.

April 19, 2009, 07:09 AM	#8
Nnobby45 Senior Member Join Date: November 20, 2004 Posts: 3,150	Variations are common, especially with HP's, including HP match ammo. .005 or even more wouldn't be unusual. If the ogives are not exactly the same, that can do it, and so can the tips where the fold comes together--such as .30 cal. 168 match ammo Some good hunting ammo, like Swift Scirocco's vary by, oh, maybe .005 to .007. Don't worry about it. If the bullets are the same, then your seating plug will contact the bullets uniformly in the same place. Measure the differences in the over all bullets lengths. That will prove informative. Then measure the difference in the loaded rounds. If the COL variation is different than the bullet variation, then maybe differences in the ogive as well as in the bullet contribute. If the ogives are different, the seating cup makes contact on different parts of the bullet, and that changes the COL. What's important is how things look on paper at the range. Consistency in the center of gravity (concentricity) is more important than the minor variations we've been discussing.