Stumped .......

[stonehands1]

Hey when you figure it out let me know. I fried my brain for days trying to figure it out. Only thing I came up with was that the comparator hole is smaller than .308. Therefore it measures different shape bullets differently. I just went through and measured every different bullet and cataloged the results for future reference.

 

[FearNoWind]

Hey when you figure it out let me know.....

and the answer is:

A measurement to the lands with a comparator can and will be different with various bullets. Different bullets have different profiles and will need to be seated further or shorter than other to actually touch the lands. The lands don't move obviously, but bullets with a shorter bearing surface will need to be seated at a different depth to touch than those that have a longer bearing surface. Pick one comparator and stick with it. Its no surprise 2 different brands of bullets have 2 different depth measurements when touching the lands. If you get a 3rd bullet, I'd bet you'd get a 3rd different reading.
__________________
Corey Schwanz
Berger Bullet Tech Support

 

[mkk]

Well it is what it is.................

I apperciate all the help, I have loaded up 5 nodes .010 apart from my measurements on the Nosler 150g. I have definatley learned that I need to measure on each brand and weight of bullet in the future. Time to go burn some powder

 

[stonehands1]

Fear no wind... I read Corey's post and it may very well be the answer but it does not explain why the distance from bolt face to lands never changes but bolt face to ogive,or what most commonly refer to as ogive (the point where the bullet becomes .308) changes with bullet shape. It could be a 2' long bullet and sticking out the end of the barrel or a 1" flat nose. The comparator will measure it at a given circumference reguardless of shape.
My comparator for .308 measures at .296. Because it is not measuring at .308 (ogive) it will measure bullets of different rates of taper (or ogive). This is the only reason I can come up with to explain it correctly.

 

[Canadian Bushman]

Fear no wind... I read Corey's post and it may very well be the answer but it does not explain why the distance from bolt face to lands never changes but bolt face to ogive,or what most commonly refer to as ogive (the point where the bullet becomes .308) changes with bullet shape. It could be a 2' long bullet and sticking out the end of the barrel or a 1" flat nose. The comparator will measure it at a given circumference reguardless of shape.
My comparator for .308 measures at .296. Because it is not measuring at .308 (ogive) it will measure bullets of different rates of taper (or ogive). This is the only reason I can come up with to explain it correctly.

If you make a comparator with simply a .308 hole that goes through it, it will be very difficult to keep square to the bullet, and it will also press onto the bullet with very little force and differently for each bullet with small changes in diameter. IE it would be difficult to use consistently.

I make all my own comparators and i make them with a smaller dia through hole with a very long shallow angle (.5-3deg) for the ogive and steeper angles (7-11deg) for the boat tails. This angle meets the face at a .308 dia. This helps the bullet remain perpindicular to the face i measure from.

If hornady's comparator is made in a similar way, you will have different contact points tangent to the angle that hornady decided to use.

Consequently your barrels lead has the same effect, between the two you will have numbers that done exactly correspond.

When used properly, you can use the tools to load your bullet however you like and never have to know any of these diameters or angles.

 

[16Bore]

If the hole in the comparator was the same as the bullet diameter, you'd never get a measurement as the bullet would pass through.

Hornady 22 insert, all kissing lands:

50 Vmax=2.884
75&80 Amax=2.924
52 Nos=2.909

The actual hole size wont really matter as long as its less than the bullet diameter. The measurement is only relative to that particular bullet. I.E. measure a 308 round with a .284 insert. Doesn't matter what the actual number is, it's only relevant to that bullet. Set your seater to what ever that number is and your round have the same BTO / COAL.

 

[FEENIX]

That is what has me stumped, I am getting 2 different measurements using different bullets.

2.240 on the Hornadys
2.190 on the Nosler

I jammed both bullets into the lands and tightened the set screw on the gauge. I know both were seated into the lands because I had to tap the bullet out with a cleaning rod.

A measurement to the lands with a comparator can and will be different with various bullets. Different bullets have different profiles and will need to be seated further or shorter than other to actually touch the lands. The lands don't move obviously, but bullets with a shorter bearing surface will need to be seated at a different depth to touch than those that have a longer bearing surface. Pick one comparator and stick with it. Its no surprise 2 different brands of bullets have 2 different depth measurements when touching the lands. If you get a 3rd bullet, I'd bet you'd get a 3rd different reading.

Corey is absolutely right! I record all my measurement (using Hornady OAL gauge) to establish a baseline during load development. Here's my latest on .300 WSM; measurements are touching the lands ...

190 Berger: COAL = 2.928"; CBTO = 2.253"
208 Hornady A-Max: COAL = 2.985"; CBTO = 2.258"
210 Berger: COAL = 2.917"; CBTO = 2.246"
215 Berger: COAL = 3.042"; CBTO = 2.277"

Effects of COAL and CBTO | Part 1 | Berger Bullets Blog

Effects of COAL and CBTO | Part 2 | Berger Bullets Blog

Hope this helps.

Ed

 

[FearNoWind]

Fear no wind... I read Corey's post and it may very well be the answer but it does not explain why the distance from bolt face to lands never changes but bolt face to ogive,or what most commonly refer to as ogive (the point where the bullet becomes .308) changes with bullet shape. It could be a 2' long bullet and sticking out the end of the barrel or a 1" flat nose. The comparator will measure it at a given circumference reguardless of shape.
My comparator for .308 measures at .296. Because it is not measuring at .308 (ogive) it will measure bullets of different rates of taper (or ogive). This is the only reason I can come up with to explain it correctly.

Well my friend, it's been explained here several time and, IMO, should be pretty clear. Not based purely on my explanation but surely on others who describe it using different verbiage. There may be some confusion beteen ogive and bearing surface and how they affect your readings - but I can't be sure so I'll simply rely on the earlier post by our Berger technical expert Corey Schwanz
and hope that gets the job done.