C.O.A.L Questions (.308)

[thepatchcable]

I'm following the reload data and it says to use 2.8 for the COAL. However, when I measure factory ammo it's around 2.880-2.890. I shoot an MR762.

Should I stick to the 2.8 COAL and work my way up or is the 2.8 just the standard for fitting all magazines?

 

[waveslayer]

I set mine to Max what the magazine will allow after I measure how far out I can seat my bullets. Depending on the bullet, some like a jump others don't. Since you're running a gasser, stick to the 2.8 ish. Otherwise you can get over pressured real quick depending on your loads. That's the quick and dirty answer

 

[thepatchcable]

I set mine to Max what the magazine will allow after I measure how far out I can seat my bullets. Depending on the bullet, some like a jump others don't. Since you're running a gasser, stick to the 2.8 ish. Otherwise you can get over pressured real quick depending on your loads. That's the quick and dirty answer

Bullet is a 155 grain hornady BTHP. It sounds like I could work my way up slowly? My case lengths are 2.005.

 

[Missalot]

It really depends on the ogive of the bullet you are using and the length of your chamber. Hornady makes tools for this. In my experience factory guns will run out of magazine length before running out of throat length.

 

[waveslayer]

Bullet is a 155 grain hornady BTHP. It sounds like I could work my way up slowly? My case lengths are 2.005.

Yes, you need to ALWAYS work up a load.

 

[thepatchcable]

Yes, you need to ALWAYS work up a load.

And when do you know you got the sweet spot? When shots are grouped nicely?

 

[waveslayer]

And when do you know you got the sweet spot? When shots are grouped nicely?

Do some research, look up OCW method, etc. Lots of info on reloading and how to come up with a load. Ladder tests, etc.. I'd give you the answer but you'll learn more by doing some good old fashion research.. you'll learn a lot

 

[straightshooter1]

I'm following the reload data and it says to use 2.8 for the COAL. However, when I measure factory ammo it's around 2.880-2.890. I shoot an MR762.

Should I stick to the 2.8 COAL and work my way up or is the 2.8 just the standard for fitting all magazines?

Bullet is a 155 grain hornady BTHP. It sounds like I could work my way up slowly? My case lengths are 2.005.

What COAL you should use depends a lot of the length of the bullet and the length of your chamber's freebore. You can choose whatever COAL you want that'll fit in your chamber and in your magazine (assuming you've no interest in hand feeding).

I've loaded 155 gr SMK Palma's that are a littler longer than the Hornady's to a COAL of 2.863 and they did just fine. I could have loaded them to 2.800, but I wanted the additional powder space for more velocity along with keeping the pressure within reason. You can load your 155's to 2.800, just be aware of the issues for the amount of powder you can use for the particular powder you may use. If you're novice at this, it'd be a good idea to hook up with a mentor to help you with deciding how to load your cartridges (maybe someone at a range where you shoot???).

And when do you know you got the sweet spot? When shots are grouped nicely?

. . . when they "consistently" group nicely.

 

[Doom]

I'm following the reload data and it says to use 2.8 for the COAL. However, when I measure factory ammo it's around 2.880-2.890. I shoot an MR762.

Should I stick to the 2.8 COAL and work my way up or is the 2.8 just the standard for fitting all magazines?

Something is amiss here. What factory ammunition are you using that measures 2..880"? No 308/7.62x51 should exceed 2.810".

 

[thepatchcable]

Something is amiss here. What factory ammunition are you using that measures 2..880"? No 308/7.62x51 should exceed 2.810".

From the tip of the bullet to the bottom of the case head is 2.880. The cartridge's themselves are 2.005

 

[waveslayer]

From the tip of the bullet to the bottom of the case head is 2.880. The cartridge's themselves are 2.005

That's the case length. Most OAL lengths are around 2.805" 2.880 should work fine.

 

[db2000]

My advice is start using “Base To Ogive” (pronounced O-Jive). Taking readings from the bullet tip can yield inconsistent and unrepeatable results.
Also, I agree with Waveslayer’s advice.

 

[thepatchcable]

My advice is start using “Base To Ogive” (pronounced O-Jive). Taking readings from the bullet tip can yield inconsistent and unrepeatable results.
Also, I agree with Waveslayer’s advice.

Thanks, I was confused between the terms. Cartridge overall length is what fits in the magazine. Case overall length is what fits in the chamber.

 

[straightshooter1]

Thanks, I was confused between the terms. Cartridge overall length is what fits in the magazine. Case overall length is what fits in the chamber.

Just to be clear . . .

Case overall length is the length of the brass casing from its base to the mouth. Whatever the maximum length it can be is determined by the length of the chambers neck area, which can vary from barrel to barrel and caliber to caliber.

COAL: Cartridge Over All Length is the length of a loaded cartridge from its base to the tip of the bullet. That length can vary by choice and is limited to either the length of one's magazine or the length of the freebore in one's barrel chamber. The latter is typically longer than the former.

CBTO: Cartridge Base To Ogive is the length from cartridge base to the ogive of the bullet and measured with a comparator that proximates the diameter of the lands in the bore.

BTO: Base To Ogive, is the reference of the measurement from the base of the bullet to that part of the ogive measured with one's comparator as above (the whole area above the bullet's bearing surface to the meplat is the ogive).

Here's a couple pica that might help FYI: