Brownells 75th Anniversary - A Shooting Heritage

Step-By-Step Reloading Part 10: Bullet Seating

We closed out 2013 by examining how to handle, meter and measure powder for the utmost consistency and accuracy. We start 2014 by looking at how to determine bullet seating depth, and different kinds of bullet seating dies. Our precision handloads are almost complete!

Seating Depth

For precision loads, one of the most important measurements to establish is how deeply the bullet should be seated into the cartridge case. Especially for high-accuracy applications with rifles, the ideal starting depth puts the bullet either touching the rifling, or almost touching it – the exact depth varies from rifle to rifle and can be discovered only through trial and error testing at the range. This starting point allows you to start making .005" to .010" increment changes to find the perfect seating depth.

Tools that help make it easier to find the perfect bullet seating depth for your rifle include the Sinclair Seating Depth Tool, the Sinclair Hex-Style Comparator, and the Sinclair Comparator with Inserts.

The Sinclair Seating Depth Tool (#749-004-650) has a rod that you insert into your action using the Delrin action guide, and two collars that help you quickly and easily determine the maximum overall length for a cartridge that fits your rifle's chamber. The unique thing about the Sinclair Seating Depth Tool is that it uses a fired case from your rifle along with the bullet of your choice so you can determine a truly custom fit for your chamber.

This maximum OAL tells you the bullet depth required to touch the rifling, and is a good starting place to begin finding the perfect seating depth for your specific rifle. Just start decreasing the bullet seating depth by the same small increments (we suggest .005" to .010") and testing the loads for accuracy.

Both the Sinclair Hex-Style Comparator (#749-002-942) and the Sinclair Comparator With Inserts (#749-002-552) help you sort a lot of loaded cartridges to eliminate variations in bullet nose length instead of measuring the cartridge overall length. Designed to measure bullets at the ogive, not the tip, these comparators help you get the maximum possible accuracy. The Hex Style will fit bullets from .17 up to .338 caliber,  and the Insert model fits bullets from .17 up to .45 caliber. The Hex-Style does not attach to your calipers, leaving them free for other tasks, while the Comparator with inserts does monopolize your calipers, and requires you to change inserts depending on which caliber you are working with.



Using both the bullet seating depth tool and a comparator together, you can make a perfect "dummy" round for your rifle. Once you determine the maximum overall cartridge length with the Sinclair Bullet Seating Depth Tool, take the same bullet and use the bullet seater to seat the bullet to that exact overall length. Then measure the cartridge with the bullet comparator from case head to the bullet ogive. It's a good idea to write this case-to-ogive length directly onto the brass case with a permanent marker, and store it with your reloading dies. This is your "zero" for die set up. You can now easily set up your bullet seating die and begin making .005" to .010" seating depth adjustments.

Seating Dies

Once you've determined the proper seating depth for the particular bullet and load you are developing, it's best to use a high-quality seating die to help maximize the accuracy potential. There are many brands and types of seating dies, with different features. Here are three styles to consider.

Standard Seater Dies

Standard Seater Dies, such as Redding, and RCBS Dies, have a solid, polished steel die body. These are the work horse seater dies: accurate, affordable, great for entry level reloaders, hunters, and folks who are interested in cranking out a high volume of reloads. They are available for rifle or pistol, in a variety of styles, including micrometer adjustable versions, and are threaded to fit onto standard reloading presses.

Threaded Chamber-Style Seating Dies

Examples of threaded Chamber-Style dies include Forster, Redding Competition, RCBS Competition and Gold Medal Dies. They are threaded, just like the Standard Seater Dies, to fit the 7/8-14 threads found on most reloading presses. But they are much more precise and adjustable than Standard Seater Dies.

Chamber-Style seater dies fully capture the case in a spring-loaded, sliding chamber sleeve, and provide support and alignment before the bullet seating actually happens. These dies are very repeatable and very accurate. They are especially popular with accuracy enthusiasts of all disciplines who reload with single stage and progressive presses. They are available in a variety of rifle calibers, but not pistol calibers.

Chamber Style "Hand Dies"

These dies are used with arbor presses. A good example of this type is the Wilson Chamber Type Bullet Seater. These Hand Dies work just like the threaded chamber-style seating dies, except the die is placed over the case and bullet for full support and alignment before seating the bullet with an arbor press (#749-007-637). These seater dies are most popular with benchrest and target shooters, and are available in a variety of rifle cartridges.

No matter which style of high-quality seater die you decide to go with, accurately measuring and setting the bullet seating depth is absolutely crucial to maximizing accuracy out of your precision handloads. And that's the final step. Once you've precisely seated the bullet to the exact depth you need, your precision handload is ready to be fired.

Roy Hill
Brownells/Sinclair Copywriter