OAL: 0.1" longer than SAAMI

[blackandgold1991]

Hi,

I measure the chamber OAL of my 308 weatherby vanguard and it was longer than SAAMI spec by 0.1". is that normal? does't mean that I should be seating the bullet higher than SAAMI recommendations?

[19K]

How did you measure it?

Do you go, no go, and field gauges? Is the rifle headspace any issue?

.1in is a significant difference. Looking online there should only be a .02 variation.

[blackandgold1991]

How did you measure it?

Do you go, no go, and field gauges? Is the rifle headspace any issue?

.1in is a significant difference. Looking online there should only be a .02 variation.

Took a sized case with just enough neck tension, but barely seated the bulet. dropped in the chamber and closed the bolt. took it out and measure both CBTO and OAL.

Longer by 0.08 to 0.1"! Measured half a dozen times!

[baih777]

Different bullets will give you different measurements.
All bullets do not measure the same.
What your seeing is only OAL. This will vary between weight and type of bullet.

Wait for randall to chime in.

[blackandgold1991]

Different bullets will give you different measurements.
All bullets do not measure the same.
What your seeing is only OAL. This will vary between weight and type of bullet.

Wait for randall to chime in.

I should clarify!

What i measured was actually the CBTO and for my NOsler CC 155gr, it was longer by 0.1" to a cartridge that was seated as per Nosler seating recommnedation.

Nosler recommends 2.8" COAL which translates to 2.2" CBTO. For my chamber I'm measuring 2.3"

[G-forceJunkie]

That doesn't measure the chamber. That measures the length of the throat.

Took a sized case with just enough neck tension, but barely seated the bulet. dropped in the chamber and closed the bolt. took it out and measure both CBTO and OAL.

Longer by 0.08 to 0.1"! Measured half a dozen times!

[blackandgold1991]

That doesn't measure the chamber. That measures the length of the throat.

Help me understand, I thought I was simulating the Hornady OAL gauge by doing this.

Thought I as pushing the ogive of the bullet to be in contact with the lands.

This I though gave the me the max CBTO to the lands

[19K]

Help me understand, I thought I was simulating the Hornady OAL gauge by doing this.

Thought I as pushing the ogive of the bullet to be in contact with the lands.

This I though gave the me the max CBTO to the lands

[LynnJr]

Your measuring for the purpose of seating bullets using your tools.
The ogive of a bullet starts at the meplat and runs into the bearing surface of your bullet so an ogive being half an inch long is extremely common.
Most comparators seem to run 0.218 - 0.219 in diameter where they make contact with the bullet regardless of the caliber.
But to your original question 0.1 off isn't a big issue unless your accuracy load won't fit into your magazine.
Edited to change olive to ogive autocorrect is very funny

[ar15barrels]

I measure the chamber OAL of my 308 weatherby vanguard and it was longer than SAAMI spec by 0.1". is that normal?

Yes.
Throats are made longer on most factory produced guns at the behest of corporate lawyers to reduce chamber pressures by giving the bullet some room to move forward and increase the effective chamber volume.

does't mean that I should be seating the bullet higher than SAAMI recommendations?

No.
Seat to your maximum allowable magazine length so you can fit cartridges into the magazine when the chamber would want a longer seating length than the magazine allows.

[ar15barrels]

Help me understand, I thought I was simulating the Hornady OAL gauge by doing this.

Thought I as pushing the ogive of the bullet to be in contact with the lands.

This I though gave the me the max CBTO to the lands

That's correct.
The throat is not part of the chamber though.

The chamber is the part where the case fits.
The throat is the part just forward of the chamber where the lands terminate into the leade and the freebore.
The leade and the freebore are generically called the "throat".

[ar15barrels]

I should clarify!

What i measured was actually the CBTO and for my NOsler CC 155gr

155's are stubby bullets and will almost never reach the lands in factory barrels while staying at magazine length.
If you want to shoot 155's, you need a custom barrel with a shorter-than-saami THROAT if you want to get close to the lands at magazine length.

[fguffey]

Help me understand, I thought I was simulating the Hornady OAL gauge by doing this.

Thought I as pushing the ogive of the bullet to be in contact with the lands.

This I though gave the me the max CBTO to the lands

You are going to have to find someone on this forum that understands methods and or techniques. There are times I want to transfer a dimension of the chamber to a die.

F. Guffey

[fguffey]

Help me understand,

There is something about this thread that looks familiar; I had a friend that built 4 magnificent rifles, he made the reamer and cut the stocks etc. When finished all 4 rifles should have been very similar but one of then shot groups like a shotgun pattern. The last person he asked was me.

He asked all of the usual questions like 'who dunit?' 'how did they do it'?, what caused it? And finally he asked me where I would start when eliminating all of the causes. I knew he would not take me seriously, but I told him anyway. He then went to the Internet for edification, after that he told me what the Internet came up with. He did not need me but that evening he shows up with his magnificent rifle, he wants me to show him what the Internet instructed him to do. Anyhow, the rifle was screwed, it had to have another barrel.

F. Guffey

[divingin]

I should clarify!

What i measured was actually the CBTO and for my NOsler CC 155gr, it was longer by 0.1" to a cartridge that was seated as per Nosler seating recommnedation.

Nosler recommends 2.8" COAL which translates to 2.2" CBTO. For my chamber I'm measuring 2.3"

As an experiment, seat an SMK and something like a Berger VLD to the same COAL (base to tip. ) Now measure CBTO (base to the point on the bullet that contacts the lands.) You'll have a lot more than a .1" difference.

OAL only matters when you're loading from a magazine (and occasionally, if you have to extract and eject a loaded round.) CBTO has an effect on accuracy. SAAMI specs are so that manufacturers are all playing from the same deck of cards. You can stray away from the SAAMI specs (assuming you know what the effect of those differences entail.) There's no SAAMI police waiting for you.