Measuring COAL

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Oddsix

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So I bought one of those Hornady oal gauges
When using the gauge with light pressure I can feel the bullet touching "something" and I get a measurement of 3.2550"but if I give it a little pressure I can get 3.4285" fairly consistently.
I notice rifling scratches on the bullet. And if I don't use a cleaning rod as a back up the bullet will not come out on its own but will come out with minimal pressure
My book says max coal is 3.34" ( which I assume is so that it may be chambered in every rifle)
My question is am I touching the rifling at that first interference or is it once I give it a little pressure?

.270 model 700 if it matters
 
As the bullet is so loose in the neck, it may not push out perfectly straight and that may be the initial resistance you feel. Then as you continue to push it straightens in the lands. I like to make certain mine is in contact with the lands...not so hard that it marks the bullet but firmly against them. It's not uncommon to have to push a bullet out with the cleaning rod after...especially with long ogive bullets.
 
I repeat the test several times to try to get a consistent number. All you're trying to do is get a repeatable number to base off of. If the bullet sticks in the rifling I consider it too far as I don't jam bullets. It won't make a difference if you're only testing jumps anyways. As to max OAL that is a SAAMI number for both ammunition and rifle mfr's to go off of to keep rifles and ammo safely compatible. You can load as long as you want provided your loaded rounds don't fall apart lol.
 
supernova said:
If the bullet sticks in the rifling I consider it too far as I don't jam bullets.
Click to expand...

With long ogive bullets in a test brass with a loose neck it's pretty common for them to stick in the riflings from the slightest bit of friction but I agree that they should not be jammed in.
 
I agree, its tough finding just the right pressure to get a consistent number without jamming a slippery bullet! Gotta put down my ham fists and get tedious he he.

sheephunter said:
With long ogive bullets in a test brass with a loose neck it's pretty common for them to stick in the riflings from the slightest bit of friction but I agree that they should not be jammed in.
Click to expand...
 
Not to derail this thread but........... I found an easier way.

Spit a sized neck about one-eighth inch in length from the top with a narrow saw blade. Put a bullet barely into the neck.
Insert this into the chamber of said rifle. Close the bolt. Extract the cartridge gently and voila you have the length.
It takes a bit of practise to get the right tension on the neck to hold the bullet upon extraction.

Works for me. As I have a dummy round like the above for every bullet in a given rifle that I shoot.
 
I found that if I use a little Red Green ingenuity and a few rubber bands I can get the tool and case to sit snugly in the chamber without having to hold it (one of those metal binder clips helps a lot), then I use a wooden dowel in through the muzzle with one hand and the metal push rod part of the tool with the other hand. This lets me seat the bullet to just kiss the lands, then back it into the case with the dowel etc. I find that if I go back and forth a few times until the seating pressure feels consistent and then lock down the set screw the measured results are very very repeatable when tested several times with the same bullet.
 
sheephunter said:
With long ogive bullets in a test brass with a loose neck it's pretty common for them to stick in the riflings from the slightest bit of friction but I agree that they should not be jammed in.
Click to expand...

I shoot Berger VLD's and they like to be deep in the rifling and you get the best accuracy.

My way of finding the max COAL is:
1) Size you case; neck or full length size. Do not prime or put powder!!
2) Seat your bullet normally
3) Extract your bullet with an impact bullet puller.
4) Insert a bullet into the case by hand. You should have enough tension on the bullet BUT not too much. Let the bullet sticks out plenty.
5) Measure COAL BEFORE inserting in the rifle.
6) Insert the round in the rifle and close the bolt.
7) Eject round be carefully not to drop it and re-measure the COAL. If it touched the rifling, you new COAL will be shorter, you will also see marks on the bullet from the rifling. That will be you MAX COAL. Most bullets will like hto be a few 0.001'' of the lands but the Berger VLD's have better accuracy touching the rifling.
8) Repeat steps 4 to 7 to make sure it's consistent. If your COAL is too long the bullet may get stuck in the barrel.

If it's a hunting application, make sure you round still fits the magazine. Also, you may want to back it out a few 0.001'' as you don't want to have a stuck bullet in your rifle when unloading your rifle while hunting!! As an example, in my 300 WSM, the 165 Nosler Accubond will touch the rifling at 2.925'' so I set the COAL at 2.918''. With the Berger VLD Hunting 168, MAX COAL is 2.955''-2.960'' but I seat the bullet to have 2.945''. Both rounds will fit my magazine.

Hope that helps!
 
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