Hello. Rather than using a comparator, I'm determining the COAL for my bolt action 30.06 Win Model 70, by placing a bullet in BARELY tight brass (fired in this same gun) and slowly closing and opening the bolt. I took 5 measurements for each of two different bullets and got remarkably close readings (within 2/1000) within each bullets markings, so I'm positive I'm getting the correct measurement to the lands. The question I have is, how much would you guys back off this measurement to determine the final live-round COAL? Thank you.
Joe

I would start .015 off the lands, or I would start with max OAL that will fit into the mag. Reduce from there.

quote:

Originally posted by steve4102:
I would start .015 off the lands, or I would start with max OAL that will fit into the mag. Reduce from there.

I am just like Steve but I start .10 off lands. Try both and see which provides the best accuracy. Best of luck!

One thing you need to determine is how much you bullet pushed into the lands. Blacken a bullet I use a magic marker after seating the bullet see how much of a mark was left on the bullet. may be .050 to .100" depending on how hard the bullet seated. on another note I would also reduce the load by 15 to 20% and work up using any seated length using that method.
Dave

.010"

it depends..
do you want to crimp? is that important to you?

i start at -.025, and then -.027 or 8, and might go as far as -.03

with barnes, i start at -.065 and go back

quote:

Originally posted by hivelosity:
One thing you need to determine is how much you bullet pushed into the lands. Blacken a bullet I use a magic marker after seating the bullet see how much of a mark was left on the bullet. may be .050 to .100" depending on how hard the bullet seated. on another note I would also reduce the load by 15 to 20% and work up using any seated length using that method.
Dave

Were do some of you come up with these numbers.

BACK OFF 15-20% I don't think so you can be asking for trouble with them numbers.

let say your loading a 270 with 4831 min load is 55grs max is 60grs so your saying back off 9 to 12grs from max AND 11grs from min. I DON'T THINK SO.

youll figure it out one of these days?

What is the magazine lenght? I would go to 0.030 inch off the lands for all hunting ammo. If the rifle likes the bullet, then the case, powder load and other fine tuning isues seem to fall in place for a 1 inch 3 shot group which is more than adequate for hunting out to 300 meters.

EDITED! Ooops...left out zeros in the seating depth as well as the long range shots!

So far .15 to .20 off the lands shoots tighter groups in my gun than does .10. .10, however seems tighter than the lengths recommended in reloading manuals. Also, not sure is .15-.20 is better than .10 in all guns and all bullet weights. I am really enjoying the testing though--big fun! More when I have it and thanks to all of you for your help.

quote:

Originally posted by Nakihunter:
What is the magazine lenght? I would go to 0.30 inch off the lands for all hunting ammo. If the rifle likes the bullet, then the case, powder load and other fine tuning isues seem to fall in place for a 1 inch 3 shot group which is more than adequate for hunting out to 30 meters.

Naki
You should work on your stalking skills.

Ooops...sorry...fixed the typos.

It is 0.030 inch seating off the lands - or 30/1000 ("thirty thou" as we say)

Hunt-Ducks....

A frequent lurker's first post. But, safety is paramount, thus, I felt the need to post.

35+ years of reloading all types of ammunition for various types of terminal performance characteristics has given me a strong need for verification of data.

Hivelosity is right on target, IF one is exceeding OAL spec's provided in a reloading manual without a corresponding reduction in powder charge.

We are talking about internal (or some prefer interior) ballistics, which is not addressed in most reloading manuals.

If one seats a projectile which results in a longer OAL than specified in a manufacturer's manual, one should strongly consider reducing the published powder charge. Loading longer than specified OAL with published powder charges WILL result in higher chamber pressures than published data supports. How high? Who knows without proper testing.

Also, please note it is not COAL that we are talking about, but, rather the OAL from the cartridge base to any given bullet's ogive and the distance to the bullet's bearing surface which initially engages the rifling. Hence, why Hivelosity marks the side of his bullets with a black marker!

If you do load on the long side of published OALs without powder charge reduction hopefully you will only see bulging brass and the barrel's throat eroding must faster than anticipated. The bad, you far exceed safe pressures for your setup and have a catastrophic failure of the barrel/action.

When deviating from a manufacturer's published data (which has undoubtedly been approved by their legal department), it is always best to reduce the powder charge and work up very slowly. All the while examining all components for any signs of high pressure.