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Overall Ammunition Length Part 2

In part one of this two-part series, we looked at how we can find the measurement for how long a round can be and still fire from a particular rifle. Today, we are going to look at how we use that measurement to then find the optimum Over All Length, or OAL, for our rifle to reach an optimum accuracy.

For this part, we will make use of a digital headspace gauge. To use this to find the OAL of your round, simply measure the split casing tool at the point of which the side of the bullet touched the rifling. Once you have that measurement, simply zero out the gauge. This will then allow the gauge to display the distance to the rifling for your reloaded ammo.


To emphasize, it is useless to measure the overall length of your round from the tip of the bullet. Instead, it’s best to use the bullet ogive, meaning the side of the bullet. However, keep in mind that increasing the overall length of your round might cause your magazine to not be able to hold and chamber the round, meaning you will have to manually load each round.

Your barrel will eventually develop enough throat erosion to increase the OAL setting for your rifle. Magnum calibers, along with several other hot cartridges, often cause considerable throat erosion after firing just a few rounds in a new barrel. Therefore, when testing the accuracy of the reloading in your hunting rifles, it’s best to start with the longest OAL that will fit in your magazine.

After that, start making changes in short increments of .003” or less until you find the OAL that shoots best. Often, reloaders will stop with a combination of the longest OAL the will both shoot accurately and fit in their magazine. However, since most hunting is done one round at a time, manually loading each round might be ok for some.

If you’re that person that is ok with handloading each round and not concerned with using a magazine, the method you find the best OAL is different. Instead of starting with the industry standard and working your way up, you start with the longest your rifle will shoot and work your way back.

Working this way, you start with your round length being at least .001” behind where the bullet touches the rifling. Then, as you test more rounds, work down in increments of .003” until you find the most accurate load.

When going this route, always remember to avoid seating the bullet long enough to actually touch the rifling. If you do this, at some point you will need to extract a loaded round and will find it rather difficult. In fact, when the bullet touches the rifling, it’s as if it was glued in place. Often, when you try to free such a round, you will pull the case away from the bullet, spilling powder inside and outside your gun.

Since reach maximum accuracy is the at the top of most reloaders must-haves for their rounds, eventually overall round length must become a factor. Just remember to always make changes to your rounds in slow and gradual increments and always take precise notes so you can have a record of what you’ve tried and what you haven’t. The idea is always to be safe, both for you and the safety of your gun.