.300 Blackout COAL?

[Virtualjim]

I'm bored on a snowy day in Ks. Pulled out the .300 BO and my Frankfort Arsenal cartridge overall length gauge.

First clamp on with the bolt in and locked. Second clamp on with a bullet held up against the rifling. Put the calipers in between and read the number. Easy right...

Overall measurement is showing 2.310.
If I haven't lost all my marbles, that is .050 thousandths longer than the SAAMI spec for this round; which is published at 2.260 max.

What am I missing here?

[Jay Andrew]

SAAMI COAL is established by the manufacturers who submit the round. It is measured from the tip of the round to the base. This measurement is especially important for proper function in a magazine/action.

Then you set the bullet out as long as you can before it touches the lands. You are setting the cartridge length based on when the bullet ogive touches the throat of the chamber. This dimension is going to vary widely based on the wear of your chamber and the geometry of the ogive.

This base to ogive measurement is an important one it you’re tinkering with loads for accuracy. Or you would like like to measure consistency of The COAL.

In short they are different measurements used for different purposes.




Reloading...it’s like knitting for men.

[JeffreyDeGraff]

Your max overall length will be different with different bullets. Each bullet has a different length and shaped nose. Max for the blackout was set due to AR magazine length restrictions.


JTD

[Virtualjim]

SAAMI COAL is established by the manufacturers who submit the round. It is measured from the tip of the round to the base. This measurement is especially important for proper function in a magazine/action.

Then you set the bullet out as long as you can before it touches the lands. You are setting the cartridge length based on when the bullet ogive touches the throat of the chamber. This dimension is going to vary widely based on the wear of your chamber and the geometry of the ogive.

This base to ogive measurement is an important one it you’re tinkering with loads for accuracy. Or you would like like to measure consistency of The COAL.

In short they are different measurements used for different purposes.




Reloading...it’s like knitting for men.

Thanks for the reply.
It's a 125 gr Nosler I'm loading.
https://load-data.nosler.com/nosler-...-AAC-125gr.pdf

Which lists 2.260 as max length for that bullet.

With my measurement (and allowing for a healthy .010 thousandths of jump) that would put me loading at 2.30 which is a whopping 40 thousandths over the company's stated max.
Factory loads measured in the 2.210 have functioned without flaw.

New enough at this that I'm wanting to make sure I don't blow something up.

[Jay Andrew]

Seating a bullet long isn’t going to cause you to blow up a gun. Unless you seat directly on the lands and your load is already particularly hot.

Usually what limits your COAL length is the Magazine or the action length. With this particular load you might also think about how much bullet shank is in the neck of the case.

I once did a load with 32 Cal 100gr XTP in my Brit 303. I could drive those suckers to 3100fps with Superformance. Trouble was there really wasn’t enough bullet shank sticking in the neck of the case to hold the bullet. I haven’t given up on the load, it think it would be a hell of a varmint load. However the same issue may apply here. You push the bullet out to far and you’ll find there’s not enough neck tension to keep it in place on chambering or under recoil.

Now if you’re in the habit of seating bullets deep, you can get yourself into trouble with pressure. So be careful going below the SAAMI COAL.


Reloading...it’s like knitting for men.

[Virtualjim]

@Jay Andrew -
Thanks for that. Just surprised that the lands are that far forward.
Appreciate the feedback.

[GraySkull]

Hold the presses! I just looked on the Hogdon reloading website and they COL there is 2.060" not 2.260"! YIKES! That's a HUGE COL difference!

http://www.hodgdonreloading.com/data/rifle

[Wes Sage]

Load to what the book states for that bullet and powder charge.
Seat just a tad deeper in needed to fit mags or your chamber, provided you aren't running the max powder charge

[Virtualjim]

Hold the presses! I just looked on the Hogdon reloading website and they COL there is 2.060" not 2.260"! YIKES! That's a HUGE COL difference!

http://www.hodgdonreloading.com/data/rifle

I found that one too and then went and looked at Noslet, SAAMI, and my Lee book. All three said 2.260. I think Hodgdon has a typo on their site.