Measure seating depth from head or shoulder?

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Forage

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Kind of new to reloading, so bear with me.

I've been reading up on adjusting bullet seating depth. Pretty much all the instructions I've found so far are to find your bullet seating depth in relation to your case head. It seems that the shoulder of the case will determine how far the bullet will be in the throat when fired, so is this measurement (shoulder to ogive) that I'm actually trying to find and adjust?

I guess if you were using brass sized to just fit your chamber then the results would be close enough, or is there something I'm not quite getting here?
 
The Cartridge Overall Length(COAL) is the most common measurement from the tip of the bullet to the flat of the case head measured usually with a micrometer, digital is easy to read.

This is one of the basic topics covered in a reloading manual.

After this and more in depth is measuring the bullet depth in relation to the lands of the rifling and use of bullet comparators.

Not all bullets tips are perfectly equal so the precision of this measurement is very good just not perfect, in the manuals the biggest reference is to COAL.

Head space is a different measurement which is a measurement involving the shoulder but is not the same as cartridge length.

Get a Lymann reloading manual , easy to read and understand, goes through all the questions you would possibly have of the reloading process.
 
Just so I'm clear:
I can use a pre-fired case to figure out a COAL that would place my bullet just short of the lands (0.01" or so). Then I can load a resized case (that has a slightly shorter distance between the case head and the shoulder) to the same COAL, and the distance from the bullet to the lands will be the same with both when chambered and fired?
 
I think you better re-read your reloading manual, or get a mentor. There are two considerations:

1) The brass must be sized sufficiently to fit in the chamber, even without a bullet. The sizing die does this by reshaping the body of the case, including but not limited to the shoulder. It also reduces the neck dia so it will hold a bullet again.

2) The brass c/w bullet must fit in the chamber (and also the magazine.) The seating die is adjustable, and allows you to set the seating depth to give you a cartridge overall length. (COL - measured from bullet tip to base, nothing to do with the shoulder.)

Given your skill level, I would discourage you from trying to seat the bullet 10 thou off the lands. Just use the cannelure on the bullet, or use the COL given in your manual.
 
When you close the bolt on a cartridge, or more importantly, when the powder ignites, the case will be pushed back against the face of the bolt. In terms of seating depth, regardless of that your other case dimensions may be, it is the measurement from base of the case to the ogive that matter in terms of managing seating depth. It is the BOLT that is the one constant. The case dimensions change during ignition and measurement off the shoulder is neither constant nor accurate.
 
Best to worry about COAL at this point, you want reliable feeding and cycling and and consistency.

Playing with fine numbers in relations to the lands is starting to get into more advanced reloading.

Walk then run , IMO you are over evaluating/thinking the loading process.If your information says a particular COAL worry about that for know, the manuals have these numbers for reasons they are for safety and reliability.

Yes, you can use a dud cartridge and it is a good idea to have to ensure proper feeding and cycling.

Listen to the folks here , baby steps are the way to go.

I can't stress enough, get a loading manual and read the entire loading process before even thinking of loading a cartridge.

Forget for now about the shoulder and worry about COAL.




Forage said:
Just so I'm clear:
I can use a pre-fired case to figure out a COAL that would place my bullet just short of the lands (0.01" or so). Then I can load a resized case (that has a slightly shorter distance between the case head and the shoulder) to the same COAL, and the distance from the bullet to the lands will be the same with both when chambered and fired?
Click to expand...
 
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