Coal

COAL does, in fact, have something to do with accuracy, in a way. In it's most commonly used form it's used to set a maximum length for your firearm. If your COAL is too long your shell may not fit in your magazine. If it's too short you may be seating the bullet too deep into the brass using up valuable case capacity. Each different bullet you reload with will have it's own optimum COAL. It really has nothing to do with how close you are to the lands in the barrel when compared with other types of bullets. But is is a very good reference when recording your reloading data for future reference. A better number would be a Comparator Length, which is the length from the bottom of the case head to the point on the bullet that contacts the rifling. This measurement is useful when loading different bullets. If one bullet shoots good at a certain CL then another bullet with a different profile will often shoot well when loaded to the same CL. X number of thousandths off the lands will most of the time be the same from bullet to bullet. I usually record both the COAL and the CL in my reloading logs.
 
Load development has 2 major steps.

Find the right powder charge for your rifle/components.
Find the best seating depth for your rifle/components.

If you're still not satisfied, then change one of your components.
 
COAL does, in fact, have something to do with accuracy, in a way. In it's most commonly used form it's used to set a maximum length for your firearm. If your COAL is too long your shell may not fit in your magazine. If it's too short you may be seating the bullet too deep into the brass using up valuable case capacity. Each different bullet you reload with will have it's own optimum COAL. It really has nothing to do with how close you are to the lands in the barrel when compared with other types of bullets. But is is a very good reference when recording your reloading data for future reference. A better number would be a Comparator Length, which is the length from the bottom of the case head to the point on the bullet that contacts the rifling. This measurement is useful when loading different bullets. If one bullet shoots good at a certain CL then another bullet with a different profile will often shoot well when loaded to the same CL. X number of thousandths off the lands will most of the time be the same from bullet to bullet. I usually record both the COAL and the CL in my reloading logs.

Load development has 2 major steps.

Find the right powder charge for your rifle/components.
Find the best seating depth for your rifle/components.

If you're still not satisfied, then change one of your components.

I'm with both these guys. I was just lazy in my answer. Sorry!
 
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