A question for those who sort their bullets.

[JFrank]

I think I am heading towards the same direction as your friend. be it bullet variance or equipment issues.

Also, if I'm going to wrap my head around this issue, which I really want to have an opinion on, I'm first going to need to know what BBTO and CBTO stand for lol

Datum!
Bullet base to ogive
Cartridge base to ogive

 

[JFrank]

Bullet base to ogive. Cartridge base to ogive.

@South Prairie jim, make sure the seating stem is cut far enough that it isn't making contact with the meplat of the bullet.

I use a Forster micro seater supposedly for VLD I have used this seater with excellent results until this box of projectiles. I believe I'll just switch to the next box and move on as all the dies are new and clean.
I'm just not sure if the difference is where the comparator touchs the bullet or where the seater touchs. Trust the seater or trust the comparator?
Or double check the press as Mike suggested? All?
J

 

[mikeeg02]

In my experience, trust the comparator. That's where you have referenced the lands measurement. And as I'm sure you know, you need to measure for each bullet. (107, vs 105 hybrid vs 105 vld etc)

270WinDude: Sorry about the CBTO vs BBTO without further explanation. Just wanted to be sure everyone knew which BTO I was referring to. And thought that was a little more common that it may be.

 

[dgeesaman]

I've encountered BBTO the same however CBTO varying as they come out of the seater, understanding that the seater will contact in a different location than the comparator which shall I trust is the question of my week?
My target says something is wrong
J
CBTO varying.008

Ouch. I switched to a Neil Jones arbor type seater and got similar variations. Then I started paying attention to the rotational position of the top and bottom sections of the die and keep them clocked with the labels lining up. Now I get +/- .001" CBTO.

 

[JFrank]

I'm in my garage loading virgin brass using a new box of 107 smk
That I've previously ensured that I have the same CBTO Datum to the lands
BBTO is the same and these are seating smoothly with CBTO on my comparator that is coming out of the seater within.0005
Go figure
J
Prepped virgin brass

 

[Bart B.]

I'm in my garage loading virgin brass using a new box of 107 smk
That I've previously ensured that I have the same CBTO Datum to the lands
BBTO is the same and these are seating smoothly with CBTO on my comparator that is coming out of the seater within.0005
Go figure
J
Prepped virgin brass

That's excellent!!! Two questions relative to my post 15:

Is the spread of virgin brass case headspace from shoulder to head that small?

How much shorter is case headspace from chamber headspace?

 

[JFrank]

That's excellent!!! Two questions relative to my post 15:

Is the spread of virgin brass case headspace from shoulder to head that small?

How much shorter is case headspace from chamber headspace?

I don't understand those questions, can you rephrase?
I'm still a Novice
J

 

[mikeeg02]

I don't understand those questions, can you rephrase?
I'm still a Novice
J

Virgin brass may not have a consistent measurement from base to .350 (6br) which is where we typically bump our shoulders back .002 from the fired case so that the bolt closes smoothly.

Your sized cases should be very consistent while new cases may have a variance.

Difference in measurement from base to the .350 mark on new vs sized cases.

 

[JFrank]

Virgin brass may not have a consistent measurement from base to .350 (6br) which is where we typically bump our shoulders back .002 from the fired case so that the bolt closes smoothly.

Your sized cases should be very consistent while new cases may have a variance.

Difference in measurement from base to the .350 mark on new vs sized cases.

Got it
I currently have a farm boy way of measuring the difference between virgin brass shoulders and fired brass shoulders, I use a 308 case over a 6 br both are relatively consistent. Fill me in'
J

 

[#40Fan]

Are you wiggling both of the cases while holding them in the caliper to insure they are settling to consistent numbers?

 

[Bart B.]

I don't understand those questions, can you rephrase?
I'm still a Novice
J

I'll explain both my questions shown in bold text:

Is the spread of virgin brass case headspace from shoulder to head that small?
Case headspace is the distance from the case head to reference diameter on case shoulder. Do you have a gauge to measure then compare them that's repeatable to .0005"?

How much shorter is case headspace from chamber headspace?
Chamber headspace is the distance from bolt face to the same reference diameter on the case shoulder. Its usually. 001" to .002" longer than a fired case's headspace.

Cartridge and chamber drawings show both. Do you have access to them?

 

[dkhunt14]

I'll explain both my questions shown in bold text:

Is the spread of virgin brass case headspace from shoulder to head that small?
Case headspace is the distance from the case head to reference diameter on case shoulder. Do you have a gauge to measure then compare them that's repeatable to .0005"?

How much shorter is case headspace from chamber headspace?
Chamber headspace is the distance from bolt face to the same reference diameter on the case shoulder. Its usually. 001" to .002" longer than a fired case's headspace.

Cartridge and chamber drawings show both. Do you have access to them?

According to Professor GUFFEY (rule no. 1) a case does not have headspace. Matt

 

[JFrank]

Are you wiggling both of the cases while holding them in the caliper to insure they are settling to consistent numbers?

Yep

 

[JFrank]

Chamber headspace is not from the case shoulder also:
Chamber headspace is the distance from the bolt-face to the same reference diameter of the chamber shoulder.

Not sure I have the tools or the smarts to measure that, I'll make that a project and get back to you
J

 

[JFrank]

Yep

I use a modified Hornday308 case that remains untrimmed

 

[Bart B.]

I use a modified Hornday308 case that remains untrimmed

Good.

Then the spread in case headspace will be the approximate spread in bullet jump distance to the rifling of all CBTO measurements are the same.