Cartridge Overall Length Questions

johnw63 · May 16, 2010, 11:53 AM

So I'm loading some 260 Remington and the books state that COL should be 2.800. How close to this do I have to get? Is it ok to be at 2.700? Or should I be shooting for 2.790 to 2.799. It seems like no matter how hard I try to make them all the exact same, there still is a + - of .005 to .010.

Also, if one bullet like "A-Max" has pointed tip, and another is a hollow point, should the COL be slightly different for those two different bullets? And what if the particular bullet you're using isn't listed in any manual?

I'm going to check my manuals, I have 5, but it is good to get feedback from guys who have been doing this for a while so thanks for any feedback.

mrawesome22 · May 16, 2010, 12:11 PM

You should be getting them close to the rifling.

brickeyee · May 16, 2010, 12:41 PM

Measuring to the ti of the bullet allows differences in the length of the bullet to throw off the measurements.

For consistent measurements you need to measure to the ogive.
Many tools are available with caliber sized holes for this purpose.

The distance to the start of the rifling is what is really important.

The distance to the tip of the bullet really only plays for magazine feeding.

steve4102 · May 16, 2010, 12:44 PM

COAL is firearm specific not manual specific. Load them to whatever works best in your firearm.

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.

ammo.crafter · May 16, 2010, 01:02 PM

I normally determine where the rifling lands/grooves begin and set OAL at .10" back as bullet should never touch rifling.

Jim243 · May 16, 2010, 01:25 PM

As Steve and Buckeyee have pointed out each bullet/rifle combination will be different. Bullets are manufactured slightly different from one mfg to another so they don't get sued for copyright or patent infringement.

Sierra 142 Gr HPBT #1742 has a "cartrage overall length" of 2.800
Hornady 140 gr A-Max #26332 has a COL of 2.785
Hornady 140 gr SST #26302 has a COL of 2.775

As you can see you have a little room to work with, the SAAMI standard is 2.800 OAL. Your rifle chamber should be 2.820 or 2.850 to accept all mfg ammo depending on how your chamber and throat has been cut.

For best results I would stay 0.020 under the max that your gun will accept. In this case it would be 2.800. Now if you gun is older and has had a lot of rounds through it, your throat of the chamber might have opened up due to erosion and might work better with a sightly longer OAL.

To check this out make a dummy round (no powder and no primer) just set the bullet in an empty case at 2.850 and do not crimp. Place the dummy in the chamber and close the bolt. If it is hard to close the bolt then stop, the round is too long for your gun. When you close the bolt on your dummy round it should push the bullet into the case and stop at the longest OAL that your gun will take. You can then extract the dummy and measure it for Max OAL in your gun. If the dummy is stuck in the chamber when you open the bolt, then use a doll rod (wood) or brass cleaning rod down the barrel to push it out.

Or you could use a doll rod or cleaning rod by itself and with the bolt closed put it all the way down the barrel to the bolt face and mark off on the cleaning rod where the front of the barrel is. Then with the bolt out, take a bullet by it's self and place it in the chamber and push it with a pencil or pen till it stops. Then take the cleaning rod and reinsert it in the barrel till it stops. Again mark on the rod the front of the barrel, remove the rod and measure between both marks and that will be your Max OAL for the bullet/rifle combo. The bullet can then easly pushed out back through the chamber.

Jim

Be sure to use a flat end of the cleaning rod and not an open end where you screw in the jag. Or just leave the jag on your cleaning rod.

mrawesome22 · May 16, 2010, 02:04 PM

Quote:

I normally determine where the rifling lands/grooves begin and set OAL at .10"

RedHawk357 · May 17, 2010, 05:56 AM

Sinclair Hex Style Bullet Comparators. My COL were all over the place until I started using this guy. I used Hornady Lock N Load OAL Gauge to determine my throat size.

May 16, 2010, 01:02 PM	#5
ammo.crafter Senior Member Join Date: June 25, 2006 Location: The Keystone State Posts: 1,970	OAL I normally determine where the rifling lands/grooves begin and set OAL at .10" back as bullet should never touch rifling. __________________ "Peace is that brief glorious moment in history when everybody stands around reloading". --Thomas Jefferson

May 16, 2010, 01:25 PM	#6
Jim243 Senior Member Join Date: January 5, 2009 Location: Just off Route 66 Posts: 5,067	As Steve and Buckeyee have pointed out each bullet/rifle combination will be different. Bullets are manufactured slightly different from one mfg to another so they don't get sued for copyright or patent infringement. Sierra 142 Gr HPBT #1742 has a "cartrage overall length" of 2.800 Hornady 140 gr A-Max #26332 has a COL of 2.785 Hornady 140 gr SST #26302 has a COL of 2.775 As you can see you have a little room to work with, the SAAMI standard is 2.800 OAL. Your rifle chamber should be 2.820 or 2.850 to accept all mfg ammo depending on how your chamber and throat has been cut. For best results I would stay 0.020 under the max that your gun will accept. In this case it would be 2.800. Now if you gun is older and has had a lot of rounds through it, your throat of the chamber might have opened up due to erosion and might work better with a sightly longer OAL. To check this out make a dummy round (no powder and no primer) just set the bullet in an empty case at 2.850 and do not crimp. Place the dummy in the chamber and close the bolt. If it is hard to close the bolt then stop, the round is too long for your gun. When you close the bolt on your dummy round it should push the bullet into the case and stop at the longest OAL that your gun will take. You can then extract the dummy and measure it for Max OAL in your gun. If the dummy is stuck in the chamber when you open the bolt, then use a doll rod (wood) or brass cleaning rod down the barrel to push it out. Or you could use a doll rod or cleaning rod by itself and with the bolt closed put it all the way down the barrel to the bolt face and mark off on the cleaning rod where the front of the barrel is. Then with the bolt out, take a bullet by it's self and place it in the chamber and push it with a pencil or pen till it stops. Then take the cleaning rod and reinsert it in the barrel till it stops. Again mark on the rod the front of the barrel, remove the rod and measure between both marks and that will be your Max OAL for the bullet/rifle combo. The bullet can then easly pushed out back through the chamber. Jim Be sure to use a flat end of the cleaning rod and not an open end where you screw in the jag. Or just leave the jag on your cleaning rod. Last edited by Jim243; May 16, 2010 at 01:38 PM.

May 17, 2010, 05:56 AM	#8
RedHawk357 Member Join Date: September 7, 2008 Location: Colorado Springs, Colorad Posts: 63	This really helped me Sinclair Hex Style Bullet Comparators. My COL were all over the place until I started using this guy. I used Hornady Lock N Load OAL Gauge to determine my throat size.

May 16, 2010, 11:53 AM	#1
johnw63 Member Join Date: February 22, 2009 Posts: 42	Cartridge Overall Length Questions So I'm loading some 260 Remington and the books state that COL should be 2.800. How close to this do I have to get? Is it ok to be at 2.700? Or should I be shooting for 2.790 to 2.799. It seems like no matter how hard I try to make them all the exact same, there still is a + - of .005 to .010. Also, if one bullet like "A-Max" has pointed tip, and another is a hollow point, should the COL be slightly different for those two different bullets? And what if the particular bullet you're using isn't listed in any manual? I'm going to check my manuals, I have 5, but it is good to get feedback from guys who have been doing this for a while so thanks for any feedback. __________________ There are two ways to conquer and enslave a nation. One is by the Sword, the other is by Debt. John Adams. 9mm, 223 Rem, 260 Rem, and Browning XT Trap.

May 16, 2010, 12:11 PM	#2
mrawesome22 Senior Member Join Date: November 9, 2005 Location: Ohio, Appalachia's foothills. Posts: 3,779	You should be getting them close to the rifling.

May 16, 2010, 12:41 PM	#3
brickeyee Senior Member Join Date: December 29, 2004 Posts: 3,351	Measuring to the ti of the bullet allows differences in the length of the bullet to throw off the measurements. For consistent measurements you need to measure to the ogive. Many tools are available with caliber sized holes for this purpose. The distance to the start of the rifling is what is really important. The distance to the tip of the bullet really only plays for magazine feeding.

May 16, 2010, 12:44 PM	#4
steve4102 Senior Member Join Date: December 23, 2005 Location: Minnesota Posts: 2,955	COAL is firearm specific not manual specific. Load them to whatever works best in your firearm. 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.