Measuring Overall Length

[horseman2]

When starting out to develop a load for a new rifle, I ran a 105 grain A-Max to the lands in a Winchester case. Comparator overall length (COAL) was 3.295.
Using Frontier scrap brass, one saved for establishing COAL and kept with that box of bullets, the COAL was 3.325. Using the Frontier Brass and another bullet, 3.330, and another 3.333.
Going back to the Winchester case, COAL for 2 more were 3.297 and 3.299.
pulling the bullets from the Frontier and trying those same bullets in the Winchester case were around 3.300.
What causes this type of variation by changing Brass?
Any similar experiences?
Perhaps the answer is to establish a standard with the brass you will be reloading with. Or throw away that piece of Frontier.

 

[Boomer]

I suspect you would see this much variation when loading with the same batch of brass. It could be accounted for by variation in how much pressure you use to seat the bullet, it could be because of differences in neck tension, or there could be that much difference in length from bullet to bullet. In any case I would think that variations of .002" would be acceptable tolerances unless you are going to extremes to make your rounds identical. Perhaps your best bet is to simply segregate your ammo into groups of equal length.

 

[H4831]

Oh dear, of all the confussion caused by modern reloading manuals that have a "C.O.A.L. figure in them!
It was so simple, when you were told to load them so they would work through the magazine. And, if you happened to have a very long magazine, be sure and not load them so long that the bullet jams so tight in the lands that it may pull out of the case, if the cartridge is removed from the chamber.

 

[horseman2]

I use the coal so I have a better idea where the bullet is in relation to the lands. Had I only used the Frontier setting, and then loaded the Winchesters with the bullet supposedly 10 thou of the lands, I would be firmly pressing the bullet of the loaded rounds into the lands. I was not using a loading manual to find the COAL but trying to find my own for this rifle.