Saturday Movies: Finding Length to Lands — Multiple Methods

Setting optimal bullet seating depth is very important for maximum accuracy. While some cartridges and barrels may deliver good accuracy with a wide range of bullet seating depths, other barrels may be more fussy, and may strongly prefer a specific seating depth, such as .006″ in the lands or .020″ off. To get this kind of precision, you need to know the exact position of the lands in your barrel. In addition, because barrel throats tend to move as the round count goes up, you should check the position of the lands regularly on a competition rifle.

Today’s Saturday Videos demonstrate a number of methods for finding Length to Lands in your rifle barrel. We start with the most common method — using the Hornady O.A.L. Gauge with a threaded modified case. With some practice, and a refined touch, this is actually very accurate. After this, we offer videos that have alternative methods, each with its pros and cons. You should find a method that works for you, that can achieve results within a couple thousandths for multiple measurements.

Finding Cartridge Length to Lands with O.A.L. Gauge

Probably the most common method to find length to lands is using a Hornady O.A.L. Gauge Tool with a comparator on a set of calipers. We regularly use this method with a custom modified case for our 6mmBR rifle. Using the technique described below, we can get results within .0015″ or so three out of four times. We do recommend taking multiple measurements. As explained below, be consistent and do NOT push the gray plastic rod too fast or with too much force.

During this measurement process, the modified case, with a bullet in its neck, is inserted in the chamber. Go slow, take your time. Here are FIVE TIPS that will help you get repeatable and reliable length-to-lands measurements with the Hornady O.A.L. Gauge:

1. Start with a clean chamber and clean barrel throat.
2. Make sure the modified case is fully screwed down and seated on the O.A.L. Gauge. It can sometimes unscrew a bit during repeated measurements.
3. Insert the modified case slowly and gently, but ensure the shoulder of the modified case is fully seated on the end of the chamber.
4. Push the gray plastic rod GENTLY. It is common for the bullet to be tilted a bit. You want to allow the bullet to self-center in the throat BEFORE you apply much pressure. Then tap a couple times and push until you feel resistance. Do NOT push too hard — that will jam the bullet in the lands.
5. Repeat the measurement at least 3 more times. If you follow our instructions, you should, typically, get a repeatable measurement, within 0.0015″ or so, 3 out of 4 times.

NOTE: We’ve seen some folks struggle to get repeatable measurements with this tool. In most cases, they were going too fast and pushing too hard on the gray rod, creating a hard jam.

Brownells — Using Hornady O.A.L. Gauge with Modified Case

This Brownells video shows how to use the modified (threaded) case for the cartridge your rifle shoots. Attach it to the O.A.L. Gauge, then insert a bullet into the case neck and slide the tool into the chamber. It takes a little practice to get consistent results. After getting the measurement in the barrel, you ascertain the length to lands using a Hornady Bullet Comparator attached to your calipers.

Making Your Own Modified Case — Threading the Case End

This helpful video from our friend Gavin Gear of UltimateReloader.com shows how to create a custom modified case to use with a Hornady O.A.L. Gauge. You need to drill out the primer pocket area, then tap and thread the bottom of the case.

Ultimate Reloader Shows 3 Ways to Find the Lands

This video shows three different ways to measure distance to lands. First Gavin Gear shows how to use a Hornady O.A.L. Gauge with Modified Case. The second methods shows how to use a bit of Loctite INSIDE the neck to secure a bullet. Be sure there is NO Loctite on the outside of the neck — you don’t want that in your chamber! You place the case with bullet into the chamber, then close bolt to seat the bullet. After waiting 5-10 minutes for the Loctite to set, you remove the cartridge gently. The third method (time-mark 16:50) is a Jam method using a bolt with the firing pin assembly and ejector removed (so there is no extra pressure on the case). Gavin notes: “The bullet ogive can be colored with a permanent marker if you want to indicate lands contact.”

About this third Jam method, ace F-Class shooter Erik Cortina posted: “My method is actually the last one that Travis showed. The one where you let the lands push bullet in. But it is neck tension dependent. I also put die wax in bullet ogive to prevent it from sticking in the lands. The method of seating bullet deeper and deeper until bolt closes is the Alex Wheeler method. As you said, there are a tons of ways to measure this.”

Finding Length to Lands the Speedy Way

Here is another method to find length to lands that can work with an unmounted barrel. This method is explained by Thomas “Speedy” Gonzales, a top gunsmith and ace benchrest shooter. Speedy drops a case with bullet seated into the chamber and then adjusts the seating depth with an inline seating die until there is no sticking or resistance felt. He can then adjust the true length to lands easily with his micrometer seating die. If you don’t have a modified case and do not want to partially disassemble your bolt to take measurement, you might want to use Speedy’s method.

Finding Length to Lands Using Bolt Movement — Primal Rights

This video shows how to remove the firing pin assembly in your bolt. This way the bolt can be used to advance a case with bullet smoothly into the chamber. Then the bullet seated in the case neck will move back to “first touch” contact position. Then extract the case slowly and measure.

The video host states: “Overall length gauges and modified cases tend to be close, but never as precise as we would like them to be. Here we describe how to measure the length to your lands in your rifle as precisely as possible, using a caliper and bullet comparator.” NOTE: The host says a store-bought Modified Case may not deliver that exact same length from case base to lands as your own fired case. That is true, but as long as the commercial Modified Case gives you repeatable results, you have a functional reference point which you can then use to test seating depths relative to that measurement.

Finding Length to Lands Using Bullet in Case With Split-Cut Neck

Here is a common method that requires no special tools. Simply take a fired (no primer), neck-sized case and split the necks down vertically with a Dremel. Done right, this will hold the bullet in place when you chamber the unloaded round. As the bullet touches the rifling it will move back. As the cartridge chambers, the bullet slides back into the case to give you length to lands. This is not super-accurate but it is probably good enough for finding the length to lands for a hunting rifle. The video maker explains: “No need to purchase gauges for this if you are willing to sacrifice one case. With a little time and patience you can get good results with this method.” Further Explanation.

How to Adjust Tension — Length and Number of Neck Cuts
Forum member Andris Silins, who uses this method, explains: “I made the neck cuts using a Dremel with a cut-off wheel. You can adjust tension two ways. First, you can make the cuts longer or shorter. Longer cuts = less tension. If you used only three cuts instead of four you would get more tension. The trick is to be gentle when you open and close the bolt. If you ram the bolt closed you may wedge the bullet into the lands. When you open the bolt it helps to keep a finger or two near by to guide the case out straight because the ejector wants to push it sideways.” READ MORE.

Finding the Lands with HK Rifleworks

This is another video that demonstrates how to disassemble the bolt so that the firing pin assembly and spring does not apply pressure on the empty case which would affect the bullet as it touches the lands. The video maker shows how to use a Brownells bolt disassembly tool to quickly take the bolt apart (3:20 time-mark). Once you have a repeatable measurement, you know exactly where is “first touch”. Then you can adjust your seating depth to be into the lands, or jumping the bullets. Many benchrest shooters like to load “into the lands”. PRS/NRL shooters and hunters will generally prefer to jump their bullets .0020″ or more.