243 win. AOL

kmaltby1 · March 11, 2009, 09:30 PM

I'm loading 243 win with 55gn nosler ballistic tips. The nosler book says that the AOL should be 2.710. The bullet doesn't seem to seat deep enough in the case. The bullet can actually be pulled out of the case by hand. Is that the right AOL?

**Unclenick** · March 11, 2009, 09:50 PM

Just for clarity, AOL is America On-Line, an Internet service provider. The term you are looking for is COL, which is Cartridge Overall Length. Some manuals and publications break "overall" into two separate initials, OA, so they abbreviate cartridge overall length as COAL. Some drop the word "cartridge" and wind up with OAL, which is probably what you saw and transposed to AOL. That's OK. Every variation possible has been tried. In truth "overall" has been a single compound word since Chaucer's day, so the single letter "O" is adequate to the purpose without the "A". I think the "C" for cartridge adds clarity to distinguish COL from CCOL (cartridge case overall length), though that is usually shortened to just CL for case length.

The COL number you have for the .243 Winchester, 2.710", is the maximum length that will still fit in a standard commercial magazine for the .243. There is nothing to stop you from making it shorter. For many rifles it turns out that the bearing surface of the bullet (the part that is cylindrical and is wide enough to fill the grooves in the bore) shoots well when its back edge is seated about one caliber deep into the case neck. On a bullet with a bearing surface shorter than one caliber, just don't seat it any deeper than the top edge of the bearing surface being even with the case mouth.

kmaltby1 · March 11, 2009, 10:44 PM

Thanks for pointing out my typing error. I'm a two finger typer and I still make errors.

**Unclenick** · March 12, 2009, 12:05 AM

It's easy to do even typing with all fingers. You just get used to typing certain combinations of letters and do it without thinking. I'll let you guess how I know?

Below is a picture with some bullet nomenclature. It might be useful to you if you don't know it already. On a bullet with no boattail, the heel still exists. By the way, when you use a specific bullet, if it has a cannelure, the manufacturer intends it to be seated so the case mouth is even with the cannelure for optional crimping. Often the manufacturers also have a COL listed with their load recommendations. Keep in mind that seating depth alters peak pressure, so figure their load minimum and maximums assume that same seating depth and the same brand of case and primer (they are all a little different and affect pressure, too).

My warning not to seat the top of the bearing surface below the top of the case mouth is not absolute. However, the case mouth can be dinged up feeding from a magazine without the bullet underneath it for support, and that can alter start pressures a bit. Also, it reduces available powder capacity and may push the bottom edge of the bearing surface of the bullet below the neck and shoulder junction on the case with some bullets. That can cause a problem if the case has been resized enough to form a donut of thickened brass at that junction which can raise pressure significantly by refusing to let go of the bullet when the pressure starts building.

E.J.W. · March 12, 2009, 10:42 AM

kmaltby1,
Unclenick has put forth some excellent info for you. Obviously a man with experience. I have a comment from my own experience and I hope Unclenick will reply as I always am open to new thoughts. This is an idea suggested to me by a fellow shooter years back.
I took a 243 casing and a intended load bullet and kept trying it in the chamber of my rifle after seating (without crimping) it in my press until I reached a point where the bullet was tight in the case and the ogive was about to touch the edge of the forcing cone or rifling. I found I could not achieve this "perfect" fit with any bullet lighter than 70 gr. So for varmit shooting that is my choice of bullet weight. The purpose of this fitting was improved accuracy as an explanation of "bullet jump" was rendered to me that day of which I remember very little. I do know my 243 loaded with 43.0 gr of IMR4350 under a Hornady 70gr SXSP (bullet no longer avail) shoots sub 1/2" groups at 100yds with only a 1" drop at 200yds. Once my supply of the 70gr SXSP is gone I will have to repeat this fitting with a new bullet.
Good luck
E.

**Unclenick** · March 12, 2009, 07:05 PM

Jump has a complex relationship with pressure. As you pull a bullet further back from being close to the lands, at first pressure drops partly because gas bypass around the bullet is increasing, but this only goes on to a point. Seating still further into the case, the fact the bullet base is is subtracting from the volume the powder has to burn in overwhelms the bypass effect and starts raising pressure again. All these changes in pressure affect bullet barrel time and can move the bullet's exit on or off a sweet spot in the barrel vibration. That's one reason adjusting seating depth can help tune a load's accuracy.

Another factor is just bullet alignment. Being close to the throat ensures the bullet isn't traveling very fast when it contacts the leade. That allows it to center better, where a fast traveling bullet will tend to swage into the bore at a slight tilt if it was not well-aligned to start with. However, if you do a good job of getting the bullet into the case without runout and the case and chamber have good axial symmetry, then you can shoot the bullet with a good bit of runup in the freebore and still get very good accuracy. Having the bullet lubricated by moly plating or by Danzac or some other coating also helps it align after a runup to the throat rather than grabbing and swaging into the bore tilted.

Being tilted in the bore, though it isn't by much, nonetheless causes accuracy issue of around one half to one MOA on the target. The NRA book Handloading documents this in the .30-06 pretty well. The slight wobble that causes a small increase in drag. Coated bullets will often exhibit a small increase in ballistic coefficient as a result of avoiding that added drag. If you keep your uncoated bullets well aligned, they can avoid it, too.

kmaltby1 · March 12, 2009, 08:22 PM

Thanks for the info everyone.

James R. Burke · March 13, 2009, 07:02 PM

No doubt Unclenick has it right. Lots of good info from him. I have learned alot from his posts. I have a .243 that I load the same bullet for my c.o.l. is 2.692, and I am sure yours will be not be the same.

a7mmnut · March 13, 2009, 07:15 PM

Additionally, the general rule of thumb for handloaders is to always seat any given bullet AT LEAST the same depth into the case neck as the diameter of the bullet.(1/4"+/-) I've also found that with all smaller diameters, there just isn't sufficient bearing surface to contact the rifling and get super accuracy with the shorter, lighter bullets. As I stated in another post, my li'l 788 will routinely shoot the 85's into 3/8"@100 yds. with a little care. I get at least 1/2" 3 shot groups with factory Federal Premiums. It's hard for me to beat that without much headache.

-7-

James R. Burke · March 15, 2009, 08:13 AM

I have a 30-06 that I worked up a load for using a 110 V-Max it is not a full diameter into the case. But it is hand fed into a Ruger No 1, and the neck tensinon is great. No problems. 3/4" 5-shot groups at 100 yards from a light sporter moving at 3712 f.p.s. You should be a full diameter in, but there are some exceptions.

March 11, 2009, 09:30 PM	#1
kmaltby1 Member Join Date: December 4, 2008 Posts: 25	243 win. AOL I'm loading 243 win with 55gn nosler ballistic tips. The nosler book says that the AOL should be 2.710. The bullet doesn't seem to seat deep enough in the case. The bullet can actually be pulled out of the case by hand. Is that the right AOL?

March 11, 2009, 09:50 PM	#2
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Just for clarity, AOL is America On-Line, an Internet service provider. The term you are looking for is COL, which is Cartridge Overall Length. Some manuals and publications break "overall" into two separate initials, OA, so they abbreviate cartridge overall length as COAL. Some drop the word "cartridge" and wind up with OAL, which is probably what you saw and transposed to AOL. That's OK. Every variation possible has been tried. In truth "overall" has been a single compound word since Chaucer's day, so the single letter "O" is adequate to the purpose without the "A". I think the "C" for cartridge adds clarity to distinguish COL from CCOL (cartridge case overall length), though that is usually shortened to just CL for case length. The COL number you have for the .243 Winchester, 2.710", is the maximum length that will still fit in a standard commercial magazine for the .243. There is nothing to stop you from making it shorter. For many rifles it turns out that the bearing surface of the bullet (the part that is cylindrical and is wide enough to fill the grooves in the bore) shoots well when its back edge is seated about one caliber deep into the case neck. On a bullet with a bearing surface shorter than one caliber, just don't seat it any deeper than the top edge of the bearing surface being even with the case mouth. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; March 11, 2009 at 10:00 PM. Reason: Corrected typo

March 12, 2009, 12:05 AM	#4
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	It's easy to do even typing with all fingers. You just get used to typing certain combinations of letters and do it without thinking. I'll let you guess how I know? Below is a picture with some bullet nomenclature. It might be useful to you if you don't know it already. On a bullet with no boattail, the heel still exists. By the way, when you use a specific bullet, if it has a cannelure, the manufacturer intends it to be seated so the case mouth is even with the cannelure for optional crimping. Often the manufacturers also have a COL listed with their load recommendations. Keep in mind that seating depth alters peak pressure, so figure their load minimum and maximums assume that same seating depth and the same brand of case and primer (they are all a little different and affect pressure, too). My warning not to seat the top of the bearing surface below the top of the case mouth is not absolute. However, the case mouth can be dinged up feeding from a magazine without the bullet underneath it for support, and that can alter start pressures a bit. Also, it reduces available powder capacity and may push the bottom edge of the bearing surface of the bullet below the neck and shoulder junction on the case with some bullets. That can cause a problem if the case has been resized enough to form a donut of thickened brass at that junction which can raise pressure significantly by refusing to let go of the bullet when the pressure starts building. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle Last edited by Unclenick; March 12, 2009 at 12:18 AM.

March 12, 2009, 10:42 AM	#5
E.J.W. Senior Member Join Date: February 26, 2008 Location: New York Posts: 171	kmaltby1, Unclenick has put forth some excellent info for you. Obviously a man with experience. I have a comment from my own experience and I hope Unclenick will reply as I always am open to new thoughts. This is an idea suggested to me by a fellow shooter years back. I took a 243 casing and a intended load bullet and kept trying it in the chamber of my rifle after seating (without crimping) it in my press until I reached a point where the bullet was tight in the case and the ogive was about to touch the edge of the forcing cone or rifling. I found I could not achieve this "perfect" fit with any bullet lighter than 70 gr. So for varmit shooting that is my choice of bullet weight. The purpose of this fitting was improved accuracy as an explanation of "bullet jump" was rendered to me that day of which I remember very little. I do know my 243 loaded with 43.0 gr of IMR4350 under a Hornady 70gr SXSP (bullet no longer avail) shoots sub 1/2" groups at 100yds with only a 1" drop at 200yds. Once my supply of the 70gr SXSP is gone I will have to repeat this fitting with a new bullet. Good luck E. __________________ You can let things happen to you -or- you can make things happen for you

March 12, 2009, 07:05 PM	#6
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Jump has a complex relationship with pressure. As you pull a bullet further back from being close to the lands, at first pressure drops partly because gas bypass around the bullet is increasing, but this only goes on to a point. Seating still further into the case, the fact the bullet base is is subtracting from the volume the powder has to burn in overwhelms the bypass effect and starts raising pressure again. All these changes in pressure affect bullet barrel time and can move the bullet's exit on or off a sweet spot in the barrel vibration. That's one reason adjusting seating depth can help tune a load's accuracy. Another factor is just bullet alignment. Being close to the throat ensures the bullet isn't traveling very fast when it contacts the leade. That allows it to center better, where a fast traveling bullet will tend to swage into the bore at a slight tilt if it was not well-aligned to start with. However, if you do a good job of getting the bullet into the case without runout and the case and chamber have good axial symmetry, then you can shoot the bullet with a good bit of runup in the freebore and still get very good accuracy. Having the bullet lubricated by moly plating or by Danzac or some other coating also helps it align after a runup to the throat rather than grabbing and swaging into the bore tilted. Being tilted in the bore, though it isn't by much, nonetheless causes accuracy issue of around one half to one MOA on the target. The NRA book Handloading documents this in the .30-06 pretty well. The slight wobble that causes a small increase in drag. Coated bullets will often exhibit a small increase in ballistic coefficient as a result of avoiding that added drag. If you keep your uncoated bullets well aligned, they can avoid it, too. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

March 11, 2009, 10:44 PM	#3
kmaltby1 Member Join Date: December 4, 2008 Posts: 25	Thanks for pointing out my typing error. I'm a two finger typer and I still make errors.

March 12, 2009, 08:22 PM	#7
kmaltby1 Member Join Date: December 4, 2008 Posts: 25	Thanks for the info everyone.

March 13, 2009, 07:02 PM	#8
James R. Burke Senior Member Join Date: January 3, 2009 Location: U.P. of Mich/Quinnesec Posts: 1,897	No doubt Unclenick has it right. Lots of good info from him. I have learned alot from his posts. I have a .243 that I load the same bullet for my c.o.l. is 2.692, and I am sure yours will be not be the same.

March 13, 2009, 07:15 PM	#9
a7mmnut Junior member Join Date: February 27, 2009 Location: NC Foothills Posts: 1,150	Additionally, the general rule of thumb for handloaders is to always seat any given bullet AT LEAST the same depth into the case neck as the diameter of the bullet.(1/4"+/-) I've also found that with all smaller diameters, there just isn't sufficient bearing surface to contact the rifling and get super accuracy with the shorter, lighter bullets. As I stated in another post, my li'l 788 will routinely shoot the 85's into 3/8"@100 yds. with a little care. I get at least 1/2" 3 shot groups with factory Federal Premiums. It's hard for me to beat that without much headache. -7-

March 15, 2009, 08:13 AM	#10
James R. Burke Senior Member Join Date: January 3, 2009 Location: U.P. of Mich/Quinnesec Posts: 1,897	I have a 30-06 that I worked up a load for using a 110 V-Max it is not a full diameter into the case. But it is hand fed into a Ruger No 1, and the neck tensinon is great. No problems. 3/4" 5-shot groups at 100 yards from a light sporter moving at 3712 f.p.s. You should be a full diameter in, but there are some exceptions.