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#6250390 - 04/06/16 07:27 PM COAL Question
GLC Offline


Registered: 02/25/09
Posts: 4109
Loc: Burleson Texas
So, I do some reloading for my hunting and LR Rifle both in 7mm08. I do my best to get best coal and even use long actions just to have enough room to get the best COAL. Now my current project, 7mm08 AR. Of course the mags are not long enough on the inside to get the proper coal. Normally shooting either Nosler or A Max. I checked out my 162 A Max longest OAL was 2.84 to fit in mag but the COAL was 2.12 and I need 2.22 to be ten thousandants off the lands so I am pretty far off. Just for grins I measured a Remington 140 grain Core Lokt. It measured 2.218 which was closer to what I needed. So my question is should I be looking more for a more "rounded" bullet and not so much "pointe". I am assuming that the BC would be terrible on that style or just go ahead and do load workups with my A MAX with a generous ramp to the lands. Range 300 to 400 rounds. Looking for pretty decent accuracy.
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#6250472 - 04/06/16 08:30 PM Re: COAL Question [Re: GLC]
FiremanJG Offline
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Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
Just load the A-maxes to mag length (if that's the bullet you want to use), and tune the powder charge to make it shoot. Nothing new under the sun jumping veey far with ARs, Tikkas, Weatherby, or really most mass produced chambered rifles.
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#6250474 - 04/06/16 08:32 PM Re: COAL Question [Re: GLC]
RiverRider Online   content
THF Trophy Hunter

Registered: 11/11/07
Posts: 6194
Loc: Wise Co.
I think you misunderstand the whole thing.

There is no magic OAL for which you aspire to chamber your rifle in order to accommodate. It's the other way around. You tailor your OAL in order to suit the chamber (and maybe a few other characteristics and/or properties of the rifle and barrel).
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God I am hating caliber threads more and more

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#6250509 - 04/06/16 08:56 PM Re: COAL Question [Re: RiverRider]
GLC Offline


Registered: 02/25/09
Posts: 4109
Loc: Burleson Texas
Originally Posted By: RiverRider
I think you misunderstand the whole thing.

There is no magic OAL for which you aspire to chamber your rifle in order to accommodate. It's the other way around. You tailor your OAL in order to suit the chamber (and maybe a few other characteristics and/or properties of the rifle and barrel).


Maybe I have misunderstood the whole thing but fortunately my bolt guns are shooting basic one holers at 100 yards with powder and COAL tuning so I think I am working in the right direction although I did not ever worry about the OAL. I just did not know what kind of difference it would make in a semi-auto with only being able to work with powder and leaving the coal alone.

Or am I totally in left field?
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#6250513 - 04/06/16 08:58 PM Re: COAL Question [Re: GLC]
ChadTRG42 Offline
THF Trophy Hunter

Registered: 09/16/09
Posts: 9393
Loc: Lewisville, TX
I'm not following your numbers on the 2.12 and 2.22. But, feeding out of an AR, you are limited by the mag length, so you will need to seat them about .010" short of mag length for reliable feeding. The A-max does a have much longer ogive to tip length. You can shoot it and see how it does, that's the tell tell. It may work fine. But, if you went to a Sierra 168 grain Matchking, there is no tip to increase the length, and the ogive to tip length is much less.

168 SMK- .665" from ogive to tip
162 A-max- .750" ogive to tip

So the 168 SMK is .085" closer to the lands than the 162 A-max at the same COAL. So, in an AR, that can be a lot. Most shooters go to a lighter bullet in an AR with a shorter ogive to tip length. 1 is for this reason you are seeing with the longer tip to ogive lengths and long jumps. 2 is to gain back some speed with the velocity loss going to an AR and generally a shorter barrel. The 162 A-max is an aggressive bullet for an AR platform, but would be a good one if you can get it to work.
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#6250731 - 04/07/16 06:48 AM Re: COAL Question [Re: GLC]
GLC Offline


Registered: 02/25/09
Posts: 4109
Loc: Burleson Texas
Thanks Chad, the 2.22 is what I need to be ten thousands off the ring lands, but because of the length of the mags the longest that I can seat the bullet is 2.12 which is a pretty big jump to the ring lands compared to my bolt guns.
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#6254209 - 04/10/16 09:52 AM Re: COAL Question [Re: GLC]
Txhillbilly Online   content
Bird Dog

Registered: 08/14/15
Posts: 439
Loc: Johnson County
What magazine do you have tha will only allow a 2.12" COAL? Every AR 10 mag I have will allow at least a 2.810" COAL.
If your bullet is touching the lands at 2.22", load a few up and try them. Sometimes you just have to test different lengths out. I can only load my 6.5-06 rounds out to 3.385" to remain magazine length, and the Berger 140 vlds are jumping .115" to the lands.It still shoots in the .3-.5 range.

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#6254338 - 04/10/16 11:55 AM Re: COAL Question [Re: GLC]
dee Offline
Extreme Tracker

Registered: 04/10/10
Posts: 4664
Loc: Red River way
If you're worried about bc the 168 Sierra mk has a much higher bc than advertised.
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#6254362 - 04/10/16 12:18 PM Re: COAL Question [Re: GLC]
ChadTRG42 Offline
THF Trophy Hunter

Registered: 09/16/09
Posts: 9393
Loc: Lewisville, TX
Originally Posted By: GLC
Thanks Chad, the 2.22 is what I need to be ten thousands off the ring lands, but because of the length of the mags the longest that I can seat the bullet is 2.12 which is a pretty big jump to the ring lands compared to my bolt guns.

Is this an ogive measurement? The case length is 2.035" (from the base to the case mouth, without a bullet), so you are saying the COAL is 2.120"? That's only .085" longer than the case itself. Somethings not right. Your COAL can not be 2.120". An ogive measurement, sure, but not the COAL. So, I'm not sure at all what's going on here. Your COAL should be around the 2.800" length.
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#6254482 - 04/10/16 02:30 PM Re: COAL Question [Re: GLC]
ChadTRG42 Offline
THF Trophy Hunter

Registered: 09/16/09
Posts: 9393
Loc: Lewisville, TX
Here's my reply from our PM, so it can also help other shooters also.

Ok. COAL and OAL are the same thing- Cartridge Overall Length= COAL or OAL=overall length. Your COAL or OAL on the round pictured is 2.913". So your max length to fit inside the AR-10 mag is 2.840". To give yourself some room to play with in feeding and reliable functioning, you will want to seat the COAL about .010" to .020" shorter, about 2.820" or 2.830". That's the realistic max COAL measurements for your AR-10.

The Hornady Comparator tool you are using is for finding your base to ogive length, not the COAL. (See the picture below). The 162 A-max has a very long ogive to tip length. For this reason, it does not make a good AR-10 bullet, since it will have such a long jump when seated at the normal 2.800"-2.820" lengths. It is seated deeper into the case occupying more powder volume, and has a long jump to the rifling. It could still shoot well, and may work fine after you shoot it and see how it does. But the 162 A-max will have to be seated at normal length (about 2.820") and have a jump to the rifling when shot from an AR-10. I'm not sure what the ringlands are, but I'm assuming you're speaking of the rifling, or the lands. This is where the ogive of the bullet makes contact with the rifling, or rifling lands of the barrel. It is an important measurement when using bullets that are sensitive to bullet jump. The 162 A-max is an aggressive ogive design, and can be sensitive to the jump to the rifling. But if this is the bullet you want to run, you will have to seat it shorter and see how it shoots.

Most of the time gas guns run a lighter weight bullet, since the ogive to tip length is shorter, and it allows you to seat the bullet at normal 2.800" length, and still have a short jump to the rifling. Any bullet with a plastic tip increases the jump. So hollow points or soft points are popular. The 308 Win doesn't have this problem that much, but starting at the 7-08, down to the 260 Rem and 243 Win have this issue with their heavy for caliber bullets and longer ogive to tip lengths.

In an AR-10, it's important to select a bullet that will allow you ease of finding a good shooting load without it being picky on seating depth. Something like a Sierra 160 or 175 grain Gameking (lead soft point) or Sierra 168 Matchking would help in an AR-10. These bullets have a shorter tip to ogive length, and are more of a tangent ogive (meaning less sensitive to bullet jump). The Berger VLD bullets would not be a good pick in an AR-10, since they have a long ogive to tip length also. Some of their Classic Hunter bullets would be good, since they are a tangent ogive design.


You can see at the picture below the bullet on the right has a more "rounded" shape between the tip and the ogive. Where the bullet on the left is more straight and comes to more of a point, or corner, at the ogive. The bullet on the left is a secant ogive, where the bullet on the right is a more tangent ogive. Tangent ogive bullets are much less seating depth sensitive, and will tolerate a jump to the rifling better, which makes them better for an AR type rifle. But the tangent ogive bullets have a lower BC, so it's a trade off. Everything in shooting is a trade off. You have to decide what is your trade off and what you want to work with.


I'd say load up some test loads with the 162 A-max and see how it shoots. That will be the deciding factor.

Read these:

http://www.bergerbullets.com/effects-of-...ve-cbto-part-1/

http://www.bergerbullets.com/effects-of-...ve-cbto-part-2/
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#6254667 - 04/10/16 06:25 PM Re: COAL Question [Re: ChadTRG42]
FiremanJG Offline
THF Celebrity

Registered: 12/16/08
Posts: 17893
Loc: Wolfe City, TX
^^Well explained, Chad^^
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#6254707 - 04/10/16 07:00 PM Re: COAL Question [Re: GLC]
GLC Offline


Registered: 02/25/09
Posts: 4109
Loc: Burleson Texas
Yep, Chad help me get straight with a lot of things including correct terminology.
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