OAL (Overall length) - explained in detail -

      I've found a number of shooters that reload who are looking to find a more complete explanation of the term "overall length" (OAL) and how to find the best length for their handloads.   Reloading manuals always record a particular OAL for each bullet they list.   However this is only a small part of the story.   It's pretty rare to see different bullet types or different bullet weights that are listed with the same OAL.   This is due to the unique curve (ogive) along the side of each bullet.   Reloading manuals recommend specific OAL dimensions according to the industry standard (SAAMI spec.).   Those loads have been tested to be safe at that particular overall length, and they should always fit in your magazine.   Finding the exact "optimum" length requires a bit more information than most reloading manuals provide.

      Factory ammo is also made according to the industry standard (SAAMI spec.) for the same reasons.   As a result, their bullets are often seated into the case at least .100" deeper than necessary.   Some rifles (especially Weatherby Magnums) have well over .250" of free-bore to the rifling.   They do this to safely reach the highest velocity possible.   On production rifles, it usually works out that if you seat your bullets closer to the rifling, your cartridges will be too long to fit in your magazine.   Finding the optimum OAL for maximum accuracy requires you to reduce the distance that the bullet travels before it contacts the rifling.   This also helps maintain concentric alignment between bullet and the bore.   That's why your accuracy improves.   If you're looking for better accuracy, your bullet needs to be well aligned as it starts down the barrel.

      Setting the OAL correctly for your "particular" chamber is the cheapest accuracy improvement there is.   However, increasing the OAL also increases chamber pressure.   To understand why chamber pressure is increased, think about this example of momentum.   A car can easily drive over a curb with a little running start; but when you are parked right up against the same curb, and you step on the gas - it requires a lot more force to start moving.   It's easy to understand why seating your bullet farther out to contact the rifling increases your chamber pressure.   When we increase the OAL, we have to work up loads with extra caution, and expect that as OAL increases, your chamber pressure will also increase.   Experienced shooters know that this is one of the most important steps for improving rifle accuracy.   The optimum length of accurate handloads will always be quite a bit longer than comparable factory loads.   Finding the optimum OAL always improves rifle accuracy.

      We have to remember that the tip of the bullet is not what contacts the barrel.   Actual contact with the rifling occurs somewhere along the ogive of the bullet, so that's where the OAL measurement needs to be made.   Shooters use several different techniques to accurately measure from the base of the case to the bullet ogive.   A few years ago, Stoney Point designed a popular tool that does a good job of making this measurement.   The picture at the right shows a special tool that I made to determine the exact OAL measurement.   This length measurement should be based on where the bullet contacts the rifling.   I have one of these modified cases for each rifle caliber that I reload.   Just take a resized case and cut 3 or 4 slots in the neck.   This is an easy project with a Dremel tool using a cut-off disk.   This makes a great chamber length gauge that will grip a bullet with just enough tension to hold it in place.   This becomes an OAL gauge for one specific caliber using one particular bullet.

      With the test bullet seated in my "split case tool", simply insert the round into your chamber.   The rifling will push the bullet deeper into the case.   Then carefully extract the round without disturbing the bullet.   After this gizmo is extracted, you can measure it from the base to the bullet ogive.   It's important to use calipers and another special tool (described below) to get an accurate measurement of this tool.   I have used the Stoney Point tool, and it works very well.   However, I still prefer using my "split case tool" to do the same thing.   This handy tool is also used for adjusting the seating depth of your dies and comparing to the OAL of your completed handloads.

     The picture at the left shows a .300 Whisper cartridge being accurately measured from the ogive, by using a special fixture that I made (see arrow) that clamps onto the calipers.   The purpose of the device is to provide a consistently accurate measurement from the "ogive" of each bullet to the cartridge base.   Due to the irregular point on most bullets, you should not try to measure the overall length to the tip of the bullets, or you will get a variety of different readings.   Except for a good magazine fit, the total length is not important.   It is important to accurately measure the overall length of your cartridges from the ogive, because this is how you determine the best seating depth and OAL.

      Keep in mind that throat erosion will cause your OAL to increase as the throat begins to wear.   Magnum calibers (and several other hot cartridges) usually cause considerable erosion after firing just a few rounds in a new barrel, but that wear will slow down a bit after the barrel is broken in.   When testing handload accuracy with hunting rifles, start experimenting with the longest OAL that will fit in your magazine.   Then start making your handloads in .003" shorter increments until you find the OAL that shoots best.   I usually settle on the longest combination that will shoot well and fit in the magazine.   If you are seeking extreme accuracy, you should start .001" behind the rifling and try reducing the OAL in .003" increments, until you come up with the most accurate load.   I always avoid seating the bullet long enough to contact the rifling, because eventually you will extract a loaded round, and you'll find that you have a bullet stuck in the rifling.   You'll become aware of this as your case pulls away from the bullet, and powder spills all over the place.

      Give this a try and see how much your accuracy improves.   It's real rewarding to see your groups tighten up, without even spending a dime to get it.   Maximum accuracy is only possible after you've found the optimum OAL for your particular chamber.