COL for an AR15 ?

rebs · November 19, 2012, 07:17 AM

How do you guys decide what COL to use ? Do use the magazine length for all bullets or go by the reloading book or work up your own for your particular rifle ? I have loaded a few 55 gr Vmax's at 2.160 and 2.250 and not seen a significant difference in accuracy, why not ?

steve4102 · November 19, 2012, 07:58 AM

Seat at least one bullet diameter (.224) into the case, fits into the mag, seat to mid cannelure if bullet has one. I rarely if ever read the manual OAL.

Why not? Could be many things, the 223/5.56 AR has a long throat, anything seated to mag length will always have a long jump.

Of all the things that affect accuracy, OAL is way down on my list, especially in a 5.56 AR.

Jimro · November 19, 2012, 09:59 PM

Load as long as you can and still use your magazine with bullets designed for the magazine. AR's aren't generally too picky about COL, and if a bullet gets set back a little during the cycle, you built in some margin for error by doing your load workup with the bullet as long as you could seat it.

Jimro

10-96 · November 20, 2012, 03:58 AM

I'm with the other guys, I don't break out the calipers or AR's or CZ 527's- just go by clip length and call it good.

rebs · November 20, 2012, 05:52 AM

In the new Hornady loading book it says they used a Colt AR 15 as their test rifle, then they go on to say what col to use for their bullets. Like all the 55 gr loaded to 2.200 and 55 gr Vmax loaded to 2.250
Why do they put that in the book ?

steve4102 · November 20, 2012, 08:18 AM

Quote:

Why do they put that in the book ?

To tell the handloader what OAL was used during testing. Some manuals find this info unnecessary and do not list the OAL tested. They instruct the handloader to find the best OAL in Their rifle. Barnes for example suggests .050 off the lands for their bullets, can't find that in any manual. Nosler lists no tested OAL.

Here is what Accurate and Ramshot have to say about OAL.

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.

JimDandy · November 20, 2012, 10:34 AM

There is also often a SAAMI maximum overall cartridge length listed. To learn what I'm doing that's what I aim at with my caliper. When I've got more confidence, I'll get the extras and actually mesure and compare and (SAFELY) experiment.

As an addtional, if you check that Hornady book some more, you'll see they offer a .224 diameter bullet recipe that can NOT be loaded to magazine length, and must be loaded singly, and this is for extreme range benchrest/competition type shooting.

rg1 · November 20, 2012, 11:38 AM

Using Hornady 55 fmj bullets in two different manufacturers AR-15's to seat the 55 fmj to touch the lands overall length would be 2.370-2.390". At that length the bullet is just about to fall out of the case. In my .223 bolt action Remington the same Hornady 55 fmj bullet touches the lands of the barrel at only 2.246". The long throat of AR-15's makes it impossible to seat bullets close to the lands except for the 75-80-90 grain match bullets which are intended to be loaded into the chamber by hand and not from the magazine. So, follow manufacturers recommended overall length or to the 2.260" maximum magazine length. You won't gain much accuracy trying to seat bullets out to the maximum 2.260" magazine length so I'd keep them to recommended lengths or close in the AR.

**Unclenick** · November 20, 2012, 12:27 PM

If you experiment with bullet seating depth you'll find accuracy sweet spots. It's not uncommon to find two, one further out near the lands, and one with the bullet seated deeper. Your best bet is to find whatever best accuracy seating depths you can identify, then use the one that is best for feed reliability if magazine fit and feed is what you are after.

Berger's method of finding best seating depths is here.

November 19, 2012, 07:17 AM	#1
rebs Senior Member Join Date: January 10, 2012 Posts: 3,881	COL for an AR15 ? How do you guys decide what COL to use ? Do use the magazine length for all bullets or go by the reloading book or work up your own for your particular rifle ? I have loaded a few 55 gr Vmax's at 2.160 and 2.250 and not seen a significant difference in accuracy, why not ?

November 19, 2012, 09:59 PM	#3
Jimro Senior Member Join Date: October 18, 2006 Posts: 7,097	Load as long as you can and still use your magazine with bullets designed for the magazine. AR's aren't generally too picky about COL, and if a bullet gets set back a little during the cycle, you built in some margin for error by doing your load workup with the bullet as long as you could seat it. Jimro __________________ Machine guns are awesome until you have to carry one.

November 20, 2012, 03:58 AM	#4
10-96 Senior Member Join Date: October 19, 2005 Location: Tx Panhandle Territory Posts: 4,159	I'm with the other guys, I don't break out the calipers or AR's or CZ 527's- just go by clip length and call it good. __________________ Rednecks... Keeping the woods critter-free since March 2, 1836. (TX Independence Day) I suspect a thing or two... because I've seen a thing or two.

November 20, 2012, 12:27 PM	#9
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	If you experiment with bullet seating depth you'll find accuracy sweet spots. It's not uncommon to find two, one further out near the lands, and one with the bullet seated deeper. Your best bet is to find whatever best accuracy seating depths you can identify, then use the one that is best for feed reliability if magazine fit and feed is what you are after. Berger's method of finding best seating depths is here. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

November 19, 2012, 07:58 AM	#2
steve4102 Senior Member Join Date: December 23, 2005 Location: Minnesota Posts: 2,955	Seat at least one bullet diameter (.224) into the case, fits into the mag, seat to mid cannelure if bullet has one. I rarely if ever read the manual OAL. Why not? Could be many things, the 223/5.56 AR has a long throat, anything seated to mag length will always have a long jump. Of all the things that affect accuracy, OAL is way down on my list, especially in a 5.56 AR.

November 20, 2012, 05:52 AM	#5
rebs Senior Member Join Date: January 10, 2012 Posts: 3,881	In the new Hornady loading book it says they used a Colt AR 15 as their test rifle, then they go on to say what col to use for their bullets. Like all the 55 gr loaded to 2.200 and 55 gr Vmax loaded to 2.250 Why do they put that in the book ?

November 20, 2012, 10:34 AM	#7
JimDandy Senior Member Join Date: August 8, 2012 Posts: 2,556	There is also often a SAAMI maximum overall cartridge length listed. To learn what I'm doing that's what I aim at with my caliper. When I've got more confidence, I'll get the extras and actually mesure and compare and (SAFELY) experiment. As an addtional, if you check that Hornady book some more, you'll see they offer a .224 diameter bullet recipe that can NOT be loaded to magazine length, and must be loaded singly, and this is for extreme range benchrest/competition type shooting.

November 20, 2012, 11:38 AM	#8
rg1 Senior Member Join Date: November 6, 2001 Posts: 1,125	Using Hornady 55 fmj bullets in two different manufacturers AR-15's to seat the 55 fmj to touch the lands overall length would be 2.370-2.390". At that length the bullet is just about to fall out of the case. In my .223 bolt action Remington the same Hornady 55 fmj bullet touches the lands of the barrel at only 2.246". The long throat of AR-15's makes it impossible to seat bullets close to the lands except for the 75-80-90 grain match bullets which are intended to be loaded into the chamber by hand and not from the magazine. So, follow manufacturers recommended overall length or to the 2.260" maximum magazine length. You won't gain much accuracy trying to seat bullets out to the maximum 2.260" magazine length so I'd keep them to recommended lengths or close in the AR.