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Using the Ladder Test to Find Your Perfect Handloads

With this ladder test, you can quickly find the right node for an optimal handloaded cartridge.

Using the Ladder Test to Find Your Perfect Handloads

The ladder method is a good way to determine safe charge weights that should deliver best accuracy with one 20-shot string. Von Benedikt found two sweet spots on this test—discounting wind effects that caused horizontal dispersion. Heavy, stiff barrels tend to produce just one node. Once you’ve determined the charge weight that will produce best results, an additional ladder test can show you the optimal seating depth.

The ladder method is the fastest, most painless route I’ve found for load development, its only drawback being the need for at least a 300-yard shooting range. But if you have access to such a distance (400 yards is even better), the ladder method enables a handloader to find an accurate, consistent and safe load in relatively few rounds. The main advantage of the ladder method is it exposes nodes in barrel vibration. For those unfamiliar with nodes, a barrel vibrates much like a pendulum swinging, although on more of a 3D plane and, of course, much, much faster. Tuning powder charges so the bullet exits the muzzle during the hesitation or pause at the end of our metaphorical pendulum swing—a node—is how good handloaders get rifles to shoot really tight groups.

Load Development Getting Started

Here’s how to run a ladder test. With your chosen propellant and projectile, begin with an appropriate loading manual’s suggested charge and load 20 or so cartridges in 1/3-grain increments (one round per charge weight) until you reach the maximum recommended charge. You’ll have to fudge a little because you can’t program electronic chargers to throw 57.33333 grains, for example, and you certainly can’t hold .01-grain increments on a mechanical scale. I generally load in the following sequence (these are hypothetical charges): 57.0 grains, 57.3 grains, 57.7 grains, 58.0 grains, and so forth. Make sure to write the charge on each cartridge case with a Sharpie marker; put them in a loading block or cartridge box in ascending order.

With your cartridges loaded and labeled, sally forth to your local long-distance shooting spot. Put up a big white target at 400 yards if possible, 300 if not. I’ve found 3x4-foot sheets of white foam core from the local arts and crafts store are perfect, but butcher paper stapled to cardboard or plywood is cheaper. With an aiming spot near the top, assume your best prone or benchrest shooting position and begin firing, starting with the lightest charge and working up to the heaviest, noting and charting the point of impact of each bullet through a good spotting scope. Be careful not to mix up the sequence. Even though it will take a little time between shots to get up from your shooting position, find the new hole through your trusty spotting scope, and mark it down on your chart. Take your time and don’t let your barrel get hot. Depending on caliber and barrel weight, I never shoot more than five shots and typically only shoot two or three before allowing the rifle to cool completely. Shooting with an overheated barrel that causes your shots to string will invalidate the test.

As you shoot, watch your brass for early pressure signs. If you begin seeing signs, stop shooting, note the point where you’ve encountered pressure, and put aside the rest of the loads to pull later. Shoot through a chronograph if you’ve got one and write down the velocity of each shot. Many chronos will save only the last 10 measurements, so if you don’t write down the velocity each time you shoot, you’ll lose some valuable data as you proceed toward the end of your test. As you work your way through the ladder test, you’ll find your shots stringing, usually vertically. Here is why it’s critical to perform such tests at long distances: At 100 yards or even 200, nodes and discrepancies in velocity have little effect on vertical point of impact. Depending on your barrel’s stiffness, the full ladder test should string somewhere between 10 and 30 inches at 400 yards. I’ve found lightweight barrels string more dramatically than stiff barrels.

ladder-load-testing-handloads-02
Garmin's new Xero C1 Pro Chronograph is an excellent, compact dopplar chronograph ideal for load development.

Downrange, reference the chart you created while shooting and number the bullet holes to correspond with the charge weights. At some point during the process, you should find three or more consecutive shots in the same area. This indicates a node in barrel vibration and a “happy place” in your powder charge. If you find a node early on, near the recommended starting charge, you’ll likely find another node as you near maximum. And you’d better hope you do so, or you’ll have to choose between lackluster velocity or repeating the test with another powder type. Assuming you’ve got a good node in a charge weight region that provides adequate velocity, you can simply pick a charge weight smack dab in the middle of those that created the node group and go with it. With that propellant and that projectile, you’re into load development in 20 rounds or less and already have a favorite charge weight for the rifle, bullet and powder you’re using.

Load Development: Optimal Bullet Seating Depth

At this point, it’s worth experimenting with bullet seating depth. For years, I just ran with conventional loading trends (seat match bullets and thin-jacketed hunting bullets close to the rifling leade and “hard” bullets such as Barnes all-copper bullets .050 or so off the rifling leade), but at one point I ran a ladder test on bullet seating depth, and the results were startling—so much so I now consider performing such a test on seating depth almost as important as doing so for powder charge weight. During that particular test, I was working with a superb albeit finicky ultralight custom rifle chambered in .270 Win. My initial ladder test with 140-grain Nosler Ballistic Tip bullets seated .015 off the rifling revealed a node centered on 55.7 grains of Reloder 19. I loaded 10 rounds with the charge and fired a series of three-shot groups. The accuracy was promising, but I wasn’t entirely happy with the results. With nothing to lose, I loaded 20 cartridges with 55.7 grains of powder—varying seating depth from engraving .020 inch into the rifling to .080 off, in .005-inch increments—and conducted another ladder test.

Predictably, the first two rounds chambered a bit too snugly for hunting purposes. Yet they both landed in the same spot, and velocity standard deviations were in the single digits. It continued that way through the first five rounds—or .025 inch of seating depth variance. Then the load came apart at the seams. By the time seating depth was .040 off the leade, the rifle was shooting all over the place, and velocity spreads jumped up to the tune of 80 fps or more between shots. Back at the loading bench, I assembled 10 more cartridges that were .010 longer than my original ladder test batch, and when I went back to the range the groups I got were everything I’d hoped for. My shooting buddy Joe Kennedy experienced the opposite. After battling to find a good 180-grain Nosler AccuBond load for his Krieger-barreled .30-06, he ran seating depth way out to .120 off the lands—and there found a magic combination that produced half-m.o.a. five-shot groups and standard deviations in the low single digits. By the time you’ve run a ladder test to determine optimal charge weight and another to determine ideal seating depth, you’ll be into your load development no more than 40 rounds, and you’ll almost certainly have achieved the best accuracy a particular bullet/propellant pairing is likely to produce. If you’re not happy, it’s time to try a different powder, projectile or both.




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