Wednesday, June 02, 2010


For those of us who piddle with such things, the Cartridge Overall Length is an important measurement to know. If you're loading for a box magazine such at the .223 Remington, you must keep your cartridge length under what will fit in the box magazine. The Sporting Arms and Ammunition Manufacturers Institute, (SAAMI) give us basic cartridge dimensions. SAAMI has set the correct overall length for the .223 Remington to be 2.260 inches.

For the .30-30 Winchester, which normally uses a flat tipped bullet, SAAMI has set the correct COAL at 2.550 inches. These are industry standards that don't takeindividual rifles into account. The fact is that all rifles are individual and if you load for a particular rifle it is prudent to know the correct overall length for your particular rifle and the particular bullet you are loading.

I'm loading .30-30 Winchester ammo for a single-shot Handi rifle and I've been playing with spitzer bullets for that rifle. Single shot rifles and pistols such as the Thompson Center Contender can use pointed bullets, where they might be dangerous in a tube magazine. So, you can seat the bullets differently, taking into account the individual peculiarities of the individual barrel.

Junior reminded me of the correct procedure for determining COAL for a particular rifle/bullet combo. For the purposes of this demonstration, we'll use the .30-30 Handi rifle I've previously discussed, and the 155 grain Hornady A-Max bullet.

According to Junior,
Partially size a fired case sizing the neck only 1/16" or so. Start a bullet. Chamber the test round letting the beginning of the lands seat the bullet. Now you know the max COAL for that particular bullet. Load 3 rounds to the max COAL minus .010" and see how they shoot.
So, I went out to the bench and partially sized a .30-30 case, then partially started the bullet with my thumb. Then I chambered the bullet, allowing the lands to seat the bullet. Then, I measured the result.

A 155 grain Hornady A-Max, jammed into the lands of my Handi Rifle measures 2.7825, 0.2325 inches longer than the SAAMI recommended COAL for that cartridge. If I seat the bullet to 2.2725 it'll be 0.010 off the lands. Hopefully that little difference will give me better accuracy than I've been getting from that rifle.

It's time to do a little loading.

1 comment:

Old NFO said...

Good review, I'd forgotten about that since I don't reload anymore... sigh... Wish I could though!