The Perfect Trim for Precision Rifle Cases

Trimming brass can be a tedious and frustrating process. Henderson Precision’s Gen 3 power trimmer makes it easier.


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Why trim brass?

Trimming brass is a necessary part of the reloading process. Brass lengthens in the neck area when sized. If it elongates enough, you can have issues with chambering. For this reason, trimming should be done AFTER resizing.

Chamfering is another part of the process. The inside chamfer assists with bullet seating while the outside chamfer has an effect on feeding.

We actually demonstrated this with Annealing Made Perfect’s AMP Press. For even more consistency, you may choose to anneal your brass. Annealing Made Perfect is more widely known for their Mark II annealer, which ensures all brass is consistently hardened. 

The perfect trim consists of correct and consistent overall length, a clean inside chamfer, clean length cut, clean outside chamfer and correct and consistent neck length.

This process should be fast and efficient—not painstaking. To determine the proper overall length, consult the SAAMI specs for your chosen cartridge. I traditionally subtract 0.020” from this number to trim to, but this can vary. 


While you can trim manually, I’ve found high-speed, power trimmers provide the cleanest cuts in the most elegant manner. We’ve used manual hand lathes, drill-mounted trimmers, the Hornady case prep center, Giraud Power trimmer, Henderson trimmer, powered press mounted trimmers and machine shop equipment for this purpose.

Using the Lee Quick Trim

There are pros and cons to all of these options. Some are more expensive than others and each offers different features.

Frankford Arsenal Drill Trimmer

The Giraud trimmer headspaces off the shoulder while the Henderson V3 trimmer has an overall length reference.

Henderson Precision Gen 3

There are also powered press mounted options like the Dillon RT-1500 and DA-3000, but they generally don’t have 3-way trimming built in. 

Trimming Cases in Bulk on the Dillon DA3000 and RT-1500

Three-way trimming—outside chamfer, inside chamfer, and trim is incredibly efficient. You reduce your brass handling to one from a possible three. 

About the Henderson Precision Powered Trimmer (Gen 3)

One of my favorite trimmers is the Henderson Precision Gen 3 Power Trimmer. We’ve reviewed this product and discussed how to set up the cutter head. 

This American-made unit allows you to adjust the outside chamfer, inside chamfer in trim length and is consistent to 0.002” with the same brand of brass. Using this trimmer is incredibly simple.

You hold the case against the collet, tighten the collet, and slide the case against the cutter. (Note there is usually a chip guard installed, but I removed it for filming purposes. 


The Henderson Precision Powered Trimmer is my choice for precision reloading, but I prefer progressive press mounted power trimmers for bulk processing. 

Henderson Precision Perfect Trim, Trimming Cases in Bulk on the Dillon CP2000 and RT-1500

Get the Gear 

Henderson Precision Gen 3 Case Trimmer

Dillon RT-1500 Case Trimmer

Hornady Case Prep Center at Midsouth Shooters Supply

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