Using Bullet Comparator

[padd54]

I just finished logging Cartridge OAL @ the Ogive for four different rifles chambered in .243win.

Here is what I came up with;

Bullet Interlock 100g Sierra GK 100g Nosler BT 70g

howa/axiom 2.251" 2.253" 2.259"

Youth howa 2.259" 2.263" 2.265"

Rem 700 sps 2.286" 2.287" 2.286"

Rem 798 sps 2.471" 2.484" 2.480" *

*bullet was barely in neck

These are averages of 5 measurements.

Please tell me what you can glean from this.
Thanks,
Ray

 

[USSR]

Ray,

The case base to bullet ogive measurement is both rifle and bullet specific. This is a PITA when loading for several rifle in the same chambering. Probably the easiest thing to do is load to an OAL for the rifle with the shortest throat, and live with the "jump" on the other rifles.

Don

 

[padd54]

Thanks for the reply.

The Howa/Axiom is my main 243, the others are for my son-in-law and my two grandsons.

I will probably load for mine, then work out a middle of the road oal for the rest.

I was just amazed at the amount of differences.

 

[Rancho Relaxo]

Wow, my results weren't anything like that. I use the cleaning rod down the barrel and leave the thumb screw on the comparator loose and push it back and forth a few times and then jam the bullet in and tighten the thumb screw. My measurements with this way have been around .001-.003 within each other. And then you have to remember that you'll have to retake measurements every 500 or 1000 rounds as the throat erodes.

 

[woods]

Very normal looking range of readings. You will get less variance with a lot of practice. The trick is to get the same amount of force pushing the bullet to the lands everytime because it is possible to push the bullet into the lands a small distance.

What works best for me is to set the bullet back into the gauge, seat the modified case fully in the chamber and with one quick low pressure movement, push the bullet to the lands with the gray rod.

Bear in mind that you need to allow for the headspace on the modified case when getting the actual distance to the lands measurement. IOW a loaded round in a fire formed case will be held against the bolt face and since you are measuring from the tip or ogive of the bullet to the base of the case, the modified case head will be at a different position in the chamber than the loaded fire formed case. Hard to explain but think about it a little and you will see what I mean.

It can make a difference of .005" to .020" easy.

 

[padd54]

I understand the concept and admit that I probably applied different pressures to seat the bullets.
What I was really wondering about was the vast differences in the readings from one gun to the next.
Especially the Rem. 700, I thought it would of had a smaller or similar readout as the Howas.
What does this say about the different chambers?
Thanks again for your patience.
Ray

 

[USSR]

What I was really wondering about was the vast differences in the readings from one gun to the next.
Especially the Rem. 700, I thought it would of had a smaller or similar readout as the Howas.
What does this say about the different chambers?

Remington's are long throated SOB's.

Don