Case Overall length question

StiffDrink

StiffDrink

Member
Rating - 0%
0   0   0
Location
Alberia
hello all


I am using the newer hornady reloading manual, and under the specific bullet data they list a COL, what I dont know is, is this a maximum or minimum figure? When I compare it to other data it is way it is way off. For example 30-06 manual says 3.185 COL for a 150 gr bt-fmj. The data that came with the lee die says the minimum COL is 3.250....so what do I do here. I am also loading .308 with the same manual, and having same issues.

SD
 
Take that published COAL figure and throw it in the garbage. The COAL dimension is wholly worthless.

The only dimension worth consideration is the loaded length to the bullet ogive. This requires a special but inexpensive tool to measure.

The ogive is where the bullet meets the rifling. Every bullet will be different. If you measure bullet length to the tip, everyone will vary even in a box of the same bullets. This is why COAL is a useless dimension.

Does the loaded round feed and extract from your chamber without sticking? Does the ammo shoot decently? If yes to both then your loaded length is fine. Forget the rest.
 
In short:

1) The COAL (or OAL) is the length of the cartridge from the bottom of the base (the 'head', or the end where the primer goes in) to the tip of the bullet. You can measure it with a set of calipers. Partly it's to make sure the loaded cartridges will fit into your magazine, but it also has a relationship with how deeply seated the bullet is in the cartridge, and how far away the bullet sits from the rifling in your barrel, and therefore has an effect on pressure.

2) It winds up being an approximation. The real measurement that matters is the CBTO (Cartridge Base to Ogive) length, which is measured from the bottom of the base to the 'ogive' on the bullet. Are you new? Don't worry about this too much yet.

3) The COAL as listed in the loading manual is what was tested in the loads. Are you new? Follow the advice of the manual exactly.

4) Set up your seating die to produce the COAL listed in the manual *FOR THE BULLET YOU ARE USING*. Don't substitute data from one bullet to another that sort of looks the same or has the same grain weight. Are you new? Follow the manual exactly for the bullet you are using from the manufacturer of the bullet. Screw out your seating die and seat a bullet, measuring the COAL with calipers, and screwing the seating die in until you get the COAL listed in the book.

5) It's not a maximum or minimum figure. It's an exact figure that you should be aiming for. But see (6) below.

6) Set your seating die to get the COAL listed in the manual. Now seat another bullet in another case and measure COAL with your calipers. You'll probably get a slightly different value. That's because the bullets aren't exactly the same. Are you new? This is probably good enough for now.

7) When you are no longer feeling new, and (6) is no longer good enough, you need a bullet comparator tool. This will measure CBTO rather than COAL, and is a much better and more consistent way of measuring things than with calipers from the base to the tip of the loaded cartridge. You will then want to start deliberately varying the CBTO (and therefore the COAL as well) to optimize your loads for your rifle. Generally, people recommend that you try to get the bullet closer to the rifling in your barrel than the basic COAL listed in your manual will give you.

The whole point of this is that, if you're new, just follow the tested data in the book for the *specific* bullet you are using; and start on the lower side of the powder ranges, too. Then work up to messing around with things like increasing the COAL to optimize accuracy when you have more experience.
 
My interpretation of COAL is Collated Over All Length as measure to the ogive.

OAL is base to tip and I do agree it is somewhat useless except when determining fit into a magazine.
 
As the others have said the OAL in the books doesn't mean much as you should be setting it up for each gun your load.

Without using fancy tools I just take a resized case and put 2 cuts in the neck parallel to the case. It acts like fingers to hold the bullet but still allow movement. For what ever bullet you use barely seat the bullet into the case. Put that in your gun a slowly close the action then slowly remove the case. If the bullet doesn't get stuck in the rifling that's a rough idea of where your rifling is and your max OAL for that gun.
 
Suputin said:
Take that published COAL figure and throw it in the garbage. The COAL dimension is wholly worthless.

The only dimension worth consideration is the loaded length to the bullet ogive. This requires a special but inexpensive tool to measure.

The ogive is where the bullet meets the rifling. Every bullet will be different. If you measure bullet length to the tip, everyone will vary even in a box of the same bullets. This is why COAL is a useless dimension.

Does the loaded round feed and extract from your chamber without sticking? Does the ammo shoot decently? If yes to both then your loaded length is fine. Forget the rest.
Click to expand...

I agree, except that you don't need any specialized tools to achieve an accurate measurement from the lands. All you need is a flat based bullet, the box of bullets you intend to load, 2 cases that can be used as dummy rounds and kept for future reference, a reasonable micrometer, and your rifle. Full length resize the two brass cases, then without priming the case, seat the flat base bullet nose down into the case, just get it started. Now chamber this cartridge in your rifle, it may take some effort to close the bolt, but ensure you close it gently without any banging. Eject the cartridge, now the length from the base of the cartridge to the flat bullet base represents an accurate measurement from the bolt face to the lands. Start the bullet you intend to load normally in the second case. Now place that bullet nose down into the muzzle of your rifle, and turn the cartridge in your fingers, keeping moderate pressure on the case. This will scribe a line at the forward edge of the bullet's bearing surface. If the line is difficult to see, color the bullet with a permanent marker and repeat. Now you can seat the bullet deeper into the case until the line scribed in the bullet matches the length of the flat base of the bullet in the first cartridge. From this point you can increase the jump or jam of the bullets of your loaded ammo to the lands. All of this data should be entered into your loading log.
 
Suputin said:
Take that published COAL figure and throw it in the garbage. The COAL dimension is wholly worthless.

The only dimension worth consideration is the loaded length to the bullet ogive. This requires a special but inexpensive tool to measure.

The ogive is where the bullet meets the rifling. Every bullet will be different. If you measure bullet length to the tip, everyone will vary even in a box of the same bullets. This is why COAL is a useless dimension.

Does the loaded round feed and extract from your chamber without sticking? Does the ammo shoot decently? If yes to both then your loaded length is fine. Forget the rest.
Click to expand...
The info they give for COL is based on there bullet, with a model number, which is the exact one I am using, I understand any other bullet measuring to the tip would be useless
 
HeavyTread said:
In short:

1) The COAL (or OAL) is the length of the cartridge from the bottom of the base (the 'head', or the end where the primer goes in) to the tip of the bullet. You can measure it with a set of calipers. Partly it's to make sure the loaded cartridges will fit into your magazine, but it also has a relationship with how deeply seated the bullet is in the cartridge, and how far away the bullet sits from the rifling in your barrel, and therefore has an effect on pressure.

2) It winds up being an approximation. The real measurement that matters is the CBTO (Cartridge Base to Ogive) length, which is measured from the bottom of the base to the 'ogive' on the bullet. Are you new? Don't worry about this too much yet.

3) The COAL as listed in the loading manual is what was tested in the loads. Are you new? Follow the advice of the manual exactly.

4) Set up your seating die to produce the COAL listed in the manual *FOR THE BULLET YOU ARE USING*. Don't substitute data from one bullet to another that sort of looks the same or has the same grain weight. Are you new? Follow the manual exactly for the bullet you are using from the manufacturer of the bullet. Screw out your seating die and seat a bullet, measuring the COAL with calipers, and screwing the seating die in until you get the COAL listed in the book.

5) It's not a maximum or minimum figure. It's an exact figure that you should be aiming for. But see (6) below.

6) Set your seating die to get the COAL listed in the manual. Now seat another bullet in another case and measure COAL with your calipers. You'll probably get a slightly different value. That's because the bullets aren't exactly the same. Are you new? This is probably good enough for now.

7) When you are no longer feeling new, and (6) is no longer good enough, you need a bullet comparator tool. This will measure CBTO rather than COAL, and is a much better and more consistent way of measuring things than with calipers from the base to the tip of the loaded cartridge. You will then want to start deliberately varying the CBTO (and therefore the COAL as well) to optimize your loads for your rifle. Generally, people recommend that you try to get the bullet closer to the rifling in your barrel than the basic COAL listed in your manual will give you.

The whole point of this is that, if you're new, just follow the tested data in the book for the *specific* bullet you are using; and start on the lower side of the powder ranges, too. Then work up to messing around with things like increasing the COAL to optimize accuracy when you have more experience.
Click to expand...

I am new, so I am trying to set it to an exact figure that is given to me in the manual, but what are my tolarences, right now I am +-0.010 at most, majority are +-0.005 from the published data. Is this good enough? With that being said aswell, I have cast .308 that I dont know where to start as faf as bullet seating is concerned, lets say I do one of the fore mentioned techniques to determine max coal, how far to I set it back from there to start testing whatmy gun likes
 
The published OAL is for the given bullet tested, and represents a value that a reloader shouldn't be less than - as the pressure can rise. There is also a SAAMI OAL which is the max OAL the industry allows for commercial ammo - some manuals show this value as well (eg Lee). You can establish your own OAL as described above, as you gain experience.
Your tolerances are fine, start at min loads as described. Don't go up to posted max unless you know what to look for as far as pressure signs. Suggest you stay a grain or two below max - giving your self some safety margin.
 
StiffDrink said:
I am new, so I am trying to set it to an exact figure that is given to me in the manual, but what are my tolarences, right now I am +-0.010 at most, majority are +-0.005 from the published data. Is this good enough? With that being said aswell, I have cast .308 that I dont know where to start as faf as bullet seating is concerned, lets say I do one of the fore mentioned techniques to determine max coal, how far to I set it back from there to start testing whatmy gun likes
Click to expand...

So I'm new, too, but probably a bit less new than you.

I had exactly the same problem you did. I loaded up a bunch of rounds and, measuring COAL with calipers, found that they had up to .015" variation. It took me all night to load about 30 rounds because I kept seating bullets, measuring COAL, pulling the bullet, adjusting the die, reseating, etc., trying to get an exact match.

I posted on another board about it, and the response I got was basically 'shut up and go fire those things'. I did that, and kept all my fingers and facial features.

What I wound up doing was getting the Hornady Bullet Comparator tool and recording the CBTO as part of my recipe rather than the COAL. This is a far more accurate way of measuring the important aspects of cartridge length.

In terms of setting up your 'ideal' COAL using the methods mentioned by others, I personally would leave that until you have a lot more experience. For now, stick with the load data in the book. Once you have a few batches of reloads done, you can worry about finding the ideal seating depth for your rifle and then *slowly* increasing COAL until it matches that value, looking for signs of excessive pressure along the way.
 
HeavyTread said:
So I'm new, too, but probably a bit less new than you.

I had exactly the same problem you did. I loaded up a bunch of rounds and, measuring COAL with calipers, found that they had up to .015" variation. It took me all night to load about 30 rounds because I kept seating bullets, measuring COAL, pulling the bullet, adjusting the die, reseating, etc., trying to get an exact match.

I posted on another board about it, and the response I got was basically 'shut up and go fire those things'. I did that, and kept all my fingers and facial features.

What I wound up doing was getting the Hornady Bullet Comparator tool and recording the CBTO as part of my recipe rather than the COAL. This is a far more accurate way of measuring the important aspects of cartridge length.

In terms of setting up your 'ideal' COAL using the methods mentioned by others, I personally would leave that until you have a lot more experience. For now, stick with the load data in the book. Once you have a few batches of reloads done, you can worry about finding the ideal seating depth for your rifle and then *slowly* increasing COAL until it matches that value, looking for signs of excessive pressure along the way.
Click to expand...

Thanks i think that helps alot. Lookin forward to putting some holes through paper. The only round i dont have a factory col to aim for is my cast bullets
 
If you want the best accuracy, forget the COAL listed in the manuals, because that COAL is not likely going to be optimum for your firearm. Start out by determining the distance to the lands with your bullet of choice, and go from there.
 
You must log in or register to reply here.
Back
Top Bottom