C.O.A.L vs Max C.O.A.L

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fivehundredlimited

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Hi all,
I'm new to reloading and after reading this post http://www.canadiangunnutz.com/forum/showthread.php/1196455-How-do-you-measure-your-c-o-a-l . I had a few questions about how to use this measurement once it has been measured.

First I notice in my reloading manual that it lists a tested at C.O.A.L for each different bullet weight/recipe. Then it also list a Max. C.O.A.L for the caliber. If I were to measure my own C.O.A.L. would this allow me to change the tested at C.O.A.L or would it allow me to change my Max C.O.A.L. listed for the caliber?

Secondly, from what I have read, if I were to seat a bullet too far, then the bullet has too much of a jump before it reaches the lands in the barrel which could cause the barrel throat to deteriorate rapidly and if I were to seat the bullet not deep enough, it could be contacting the lands in the barrel before it is fired and prevent gases from escaping the chamber and cause pressure issues which could be dangerous.

If the above statement is true...it would seem as if measuring my C.O.A.L would be very important and pretty much a necessity? Or can I safely reload according to my manual's tested at C.O.A.L. without causing unnecessary deterioration to my barrel?
Fivehundred
 
If in doubt, go with what the manual says.

What are you shooting? (Caliber and bullet)

From what I know, jump or jam makes little difference on throat life.

Secondly, when people say "seating the bullets long/far", then normally refer to longer then usual COAL. And "seating deep or short" refers to shorter COAL. Just so everyone is using the same lingo.

Third, the effective max charge depends on the COAL. Say you have a 308, with an effective max of 44gr of varget behind a 168gr bullet seated just touching the lands. If you jam it 0.050", the pressure will increase. If you jump it 0.050", the pressure will also increase.

For VLDs, they have a sweet spot somewhere between 0.120" jump and 0.030 jam. First you find that sweet spot with a reduced powder charge, and then you can work up to fine tune the load and find your effective max for that combination.
 
fivehundredlimited said:
Hi all,
I'm new to reloading and after reading this post http://www.canadiangunnutz.com/forum/showthread.php/1196455-How-do-you-measure-your-c-o-a-l . I had a few questions about how to use this measurement once it has been measured.

First I notice in my reloading manual that it lists a tested at C.O.A.L for each different bullet weight/recipe. Then it also list a Max. C.O.A.L for the caliber. If I were to measure my own C.O.A.L. would this allow me to change the tested at C.O.A.L or would it allow me to change my Max C.O.A.L. listed for the caliber?

Secondly, from what I have read, if I were to seat a bullet too far, then the bullet has too much of a jump before it reaches the lands in the barrel which could cause the barrel throat to deteriorate rapidly and if I were to seat the bullet not deep enough, it could be contacting the lands in the barrel before it is fired and prevent gases from escaping the chamber and cause pressure issues which could be dangerous.

If the above statement is true...it would seem as if measuring my C.O.A.L would be very important and pretty much a necessity? Or can I safely reload according to my manual's tested at C.O.A.L. without causing unnecessary deterioration to my barrel?
Fivehundred
Click to expand...

Whatever you are reading, stop reading that nonsense. I ignore any COL posted in any manual or on any website. I find the distance to the lands in my rifle with a given bullet, and base my COL on that measurement, and on the length of a loaded cartridge that will both fit the magazine, and with cycle smoothly through the action.
 
It's easy to do when you are new to the reloading game but on this topic you are over thinking it. OAL shorter than the maximum won't do any damage to your rifle (I'd be curious where you found this information). Even with bullets at maximum length, jammed into the lands, unless you are running loads at maximum pressures I find it hard to believe that you would have any issues.

The cartridge lengths in the manuals are the most useless information in them. The only thing that I can think these stats are useful for is for understanding the seating used to develop the published pressures and MVs.

Find the max. OAL Using the methods you have read about (Hornady gauge, dummy round, slit case, etc.) and start testing what your rifle likes.
 
Thanks guys,
I tried to find the webpage I read that info from, but it was month or so ago now and couldn't find it. I was planning to use a ladder test to find my best load, but it sounds like I should get a Hornady gauge first, then do a ladder test from there and try it at different OALs?
 
fivehundredlimited said:
Thanks guys,
I tried to find the webpage I read that info from, but it was month or so ago now and couldn't find it. I was planning to use a ladder test to find my best load, but it sounds like I should get a Hornady gauge first, then do a ladder test from there and try it at different OALs?
Click to expand...

Good plan. The Hornady gauge isn't really needed but is a nice-to-have. Start at 10 thousandths off the lands when doing your load test and once you have your best loads, start playing with length. Reduce the number of variables that you are changing at any one time or it's easy to get lost. The type of bullet and the type of powder can also have a big influence. It's all part of the fun. Good luck.
 
stubblejumper said:
Whatever you are reading, stop reading that nonsense. I ignore any COL posted in any manual or on any website. I find the distance to the lands in my rifle with a given bullet, and base my COL on that measurement, and on the length of a loaded cartridge that will both fit the magazine, and with cycle smoothly through the action.
Click to expand...

With a new rifle, I load the first round very long and chamber it. this will leave rifling marks on the bullet. I put that round aside and seat the bullet deeper. The length of the rifling marks suggest the next step. Each quarter turn of the seater stem is about 12 thou. So I seat the bullet deeper, and see how much mark there is from the rifling. That round is put aside. Then I seat the next one a bit deeper. Eventually I get to the point where I transition form rifling marks to no marks. I record that OAL as the reference distance.

If I want the bullets in the rifling, I seat them out 10 thou from that. If I want the bullets off the rifling, I seat them 20 thou deeper.

Once I set the correct OAL, I load the ammo and run through the rounds that were all put aside when calculating the OAL.
 
I was wondering if the coal on the reloading data were more about amount of air space between the powder and the base of the bullet?
The less the air space the greater the pressure?
 
The type of bullet and the type of powder can also have a big influence.
Click to expand...

My experience has taught me that finding the optimum powder/bullet combination for a given rifle, goes much farther toward finding the optimum load, than simply trying a single powder/'bullet combination, and experimenting with the COL, or the powder charge. Some people are so determined to use a specific powder/bullet combination, that they waste a lot of time and components trying to find a great load, by varying the COL and the powder charge weight, when they would be far better off trying another bullet, or another powder.

Paatz said:
I was wondering if the coal on the reloading data were more about amount of air space between the powder and the base of the bullet?
The less the air space the greater the pressure?
Click to expand...

The COL in a manual may be the SAAMI COL or it may simply be the COL that they chose based on the throat of the particular rifle. As for the less the air space the greater the pressure, that isn't always true. A bullet seated .030" off of the lands will usually produce less pressure than a bullet seated against the lands, even though it has less air space.
 
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Paatz said:
I was wondering if the coal on the reloading data were more about amount of air space between the powder and the base of the bullet?
The less the air space the greater the pressure?
Click to expand...

I worked in a lab that developed loads that got published in manuals. The published data referred to the rifle /barrel we used. COAL would have to developed for your rifle. If you used the published COAL there is no guarantee it would fit YOUR magazine or not be jammed into the rifling of YOUR chamber.
 
COAL given in loading manual is typically the minimum overall length that is safe for a given bullet powder combination. Heavy bullets are typically longer so this becomes more important. Going less than MIN COAL can unsafely increase the pressure on ignition and if it is bad enough it MAY cause damage to the gun and anyone around it. Obviously there is a margin for error but as a general principle you should never load less than the Min COAL as it can be dangerous. This is especially so if you are loading to maximum powder levels.

MAX COAL is a different issue. The max length is about what will reliably feed into the chamber. Each gun is a little different but if the cartridge is less than the MAX COAL it will normally feed properly. If a bullet gets too long it can jamb. Annoying but not dangerous per say. There is one rinkle to this if a cartridge jams it may drive the bullet back into the case thus possibly moving it into the first category.

Personally it tend to make my cartridges with a COAL of MIN plus about 2/3rds of the difference between MIN and MAX. Most of the time this feeds very well and there is no pressure risk. 45ACP in a 1911 tends to work best at the longer end of the range. Each gun is a little different but I find my method almost always works reliably.

Load on.
 
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