COAL or CBTO

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COAL = "cartridge overall length". That is the length of the cartridge, from base to the tip of the bullet.

CBTO = "cartridge base to ogive". That is the length between the base of the cartridge to the ogive of the bullet.

Both measurements are useful. CBTO is good for measuring seating depth because you can remove the inconsistencies introduced by the bullet tip. COAL, being the overall physical length, is important in regards to determining magazine clearance and adherence to load and caliber specs.
 
ParallelCode said:
COAL = "cartridge overall length". That is the length of the cartridge, from base to the tip of the bullet.

CBTO = "cartridge base to ogive". That is the length between the base of the cartridge to the ogive of the bullet.

Both measurements are useful. CBTO is good for measuring seating depth because you can remove the inconsistencies introduced by the bullet tip. COAL, being the overall physical length, is important in regards to determining magazine clearance and adherence to load and caliber specs.
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Thank you so much, I couldn't put these together, thanks again.
 
ParallelCode said:
COAL = "cartridge overall length". That is the length of the cartridge, from base to the tip of the bullet.

CBTO = "cartridge base to ogive". That is the length between the base of the cartridge to the ogive of the bullet.

Both measurements are useful. CBTO is good for measuring seating depth because you can remove the inconsistencies introduced by the bullet tip. COAL, being the overall physical length, is important in regards to determining magazine clearance and adherence to load and caliber specs.
Click to expand...
Funny but, I was taught wrong, which is actually right. I was taught COAL is Cartridge Overall Average Length. My uncle told me it's always going to be an average because no two bullets are going to be EXACTLY the same, from base to tip, or ogive to tip, or ogive to base... they're just going to have differences, sometimes very slight and sometimes fairly pronounced. So, you seat to an average of several samples and check to make sure none are too short or too long for your application during your final spot-check. OAL is Overall Length but, that doesn't make sense if the A in COAL is Average, nor does it make sense because overall is one word in the English language*, so why split it out to make an acronym for just this one application? Don't make sense to do that. So why isn't OAL Overall Average Length and the cartridge measure COL, for Cartridge Overall Length? Well, COL is Cartridge Overall Length - in some older manuals - and should be everywhere except that would be a single, finite number and since no two bullets or cases are EXACTLY alike, you'd have to chase that single digit on every seating, and that's just not smart or practical; or, you'd have to settle for a range of COL's - an Average.

Sorry to seem pedantic but some acronyms in gun parlance just make sense and some you just have to learn because they're part of gun lore.

* overall (adv.): Middle English over-al, from everywhere," Old English phrase ofer eall "everywhere, in every part or place," from ofer "over" (see over) + eall (see all). The original sense seems to be obsolete. The meaning "including everything, taking all into consideration" is from 1894.
from the Online Etymology Dictionary, https://www.etymonline.com/
 
Base to ogive measurements are usually more accurate and more of an advantage when "seating off the lands" where the distance from the ogive to the rifling is used as a guide for best accuracy.
 
Limited experience here, but I usually see CBTO used when the discussion is about rifle ammo, whereas it's generally not used much in handgun discussions.
 
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barnfrog said:
Limited experience here, but I usually see CBTO used when the discussion is about rifle ammo, whereas it's generally not used much in handgun discussions.
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The only practical application for handgun is to find the max/min seating depth for a bullet to fit a specific gun, or a group of guns, without resorting to trial-and-error. Most folks prefer trial-and-error to math-and-measuring which is why you don't hear much about it with handguns.
 
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GeoDudeFlorida said:
Funny but, I was taught wrong, which is actually right. I was taught COAL is Cartridge Overall Average Length. My uncle told me it's always going to be an average because no two bullets are going to be EXACTLY the same, from base to tip, or ogive to tip, or ogive to base... they're just going to have differences, sometimes very slight and sometimes fairly pronounced. So, you seat to an average of several samples and check to make sure none are too short or too long for your application during your final spot-check. OAL is Overall Length but, that doesn't make sense if the A in COAL is Average, nor does it make sense because overall is one word in the English language*, so why split it out to make an acronym for just this one application? Don't make sense to do that. So why isn't OAL Overall Average Length and the cartridge measure COL, for Cartridge Overall Length? Well, COL is Cartridge Overall Length - in some older manuals - and should be everywhere except that would be a single, finite number and since no two bullets or cases are EXACTLY alike, you'd have to chase that single digit on every seating, and that's just not smart or practical; or, you'd have to settle for a range of COL's - an Average.

Sorry to seem pedantic but some acronyms in gun parlance just make sense and some you just have to learn because they're part of gun lore.

* overall (adv.): Middle English over-al, from everywhere," Old English phrase ofer eall "everywhere, in every part or place," from ofer "over" (see over) + eall (see all). The original sense seems to be obsolete. The meaning "including everything, taking all into consideration" is from 1894.
from the Online Etymology Dictionary, https://www.etymonline.com/
Click to expand...
I love etymology. For some reason I find it fascinating. I even took Latin for 2 years in Junior high.

I've never seen that website. Thanks.
 
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